Removed temporary memory from the API

It was intended to make the API easier to use, but various automatic garbage collection all had flaws, and making the application periodically clean up temporary memory added cognitive load to using the API, and in many cases was it was difficult to restructure threaded code to handle this.

So, we're largely going back to the original system, where the API returns allocated results and you free them.

In addition, to solve the problems we originally wanted temporary memory for:
* Short strings with a finite count, like device names, get stored in a per-thread string pool.
* Events continue to use temporary memory internally, which is cleaned up on the next event processing cycle.

include/SDL3/SDL_video.h

@@ -356,7 +356,7 @@ extern SDL_DECLSPEC int SDLCALL SDL_GetNumVideoDrivers(void);
  *
  * \sa SDL_GetNumVideoDrivers
  */
-extern SDL_DECLSPEC_TEMP const char * SDLCALL SDL_GetVideoDriver(int index);
+extern SDL_DECLSPEC const char * SDLCALL SDL_GetVideoDriver(int index);
 
 /**
  * Get the name of the currently initialized video driver.
@@ -373,7 +373,7 @@ extern SDL_DECLSPEC_TEMP const char * SDLCALL SDL_GetVideoDriver(int index);
  * \sa SDL_GetNumVideoDrivers
  * \sa SDL_GetVideoDriver
  */
-extern SDL_DECLSPEC_TEMP const char * SDLCALL SDL_GetCurrentVideoDriver(void);
+extern SDL_DECLSPEC const char * SDLCALL SDL_GetCurrentVideoDriver(void);
 
 /**
  * Get the current system theme.
@@ -390,11 +390,11 @@ extern SDL_DECLSPEC SDL_SystemTheme SDLCALL SDL_GetSystemTheme(void);
  * \param count a pointer filled in with the number of displays returned, may
  *              be NULL.
  * \returns a 0 terminated array of display instance IDs or NULL on failure;
- *          call SDL_GetError() for more information.
+ *          call SDL_GetError() for more information. This should be freed with SDL_free() when it is no longer needed.
  *
  * \since This function is available since SDL 3.0.0.
  */
-extern SDL_DECLSPEC_TEMP const SDL_DisplayID * SDLCALL SDL_GetDisplays(int *count);
+extern SDL_DECLSPEC_FREE SDL_DisplayID * SDLCALL SDL_GetDisplays(int *count);
 
 /**
  * Return the primary display.
@@ -448,7 +448,7 @@ extern SDL_DECLSPEC SDL_PropertiesID SDLCALL SDL_GetDisplayProperties(SDL_Displa
  *
  * \sa SDL_GetDisplays
  */
-extern SDL_DECLSPEC_TEMP const char * SDLCALL SDL_GetDisplayName(SDL_DisplayID displayID);
+extern SDL_DECLSPEC const char * SDLCALL SDL_GetDisplayName(SDL_DisplayID displayID);
 
 /**
  * Get the desktop area represented by a display.
@@ -551,13 +551,13 @@ extern SDL_DECLSPEC float SDLCALL SDL_GetDisplayContentScale(SDL_DisplayID displ
  * \param count a pointer filled in with the number of display modes returned,
  *              may be NULL.
  * \returns a NULL terminated array of display mode pointers or NULL on
- *          failure; call SDL_GetError() for more information.
+ *          failure; call SDL_GetError() for more information. This is a single allocation that should be freed with SDL_free() when it is no longer needed.
  *
  * \since This function is available since SDL 3.0.0.
  *
  * \sa SDL_GetDisplays
  */
-extern SDL_DECLSPEC_TEMP const SDL_DisplayMode * const * SDLCALL SDL_GetFullscreenDisplayModes(SDL_DisplayID displayID, int *count);
+extern SDL_DECLSPEC_FREE SDL_DisplayMode ** SDLCALL SDL_GetFullscreenDisplayModes(SDL_DisplayID displayID, int *count);
 
 /**
  * Get the closest match to the requested display mode.
@@ -576,16 +576,17 @@ extern SDL_DECLSPEC_TEMP const SDL_DisplayMode * const * SDLCALL SDL_GetFullscre
  *                     for the desktop refresh rate.
  * \param include_high_density_modes boolean to include high density modes in
  *                                   the search.
- * \returns a pointer to the closest display mode equal to or larger than the
- *          desired mode, or NULL on failure; call SDL_GetError() for more
- *          information.
+ * \param mode a pointer filled in with the closest display mode equal to or larger than the
+ *          desired mode.
+ * \returns 0 on success or a negative error code on failure; call
+ *          SDL_GetError() for more information.
  *
  * \since This function is available since SDL 3.0.0.
  *
  * \sa SDL_GetDisplays
  * \sa SDL_GetFullscreenDisplayModes
  */
-extern SDL_DECLSPEC_TEMP const SDL_DisplayMode * SDLCALL SDL_GetClosestFullscreenDisplayMode(SDL_DisplayID displayID, int w, int h, float refresh_rate, SDL_bool include_high_density_modes);
+extern SDL_DECLSPEC int SDLCALL SDL_GetClosestFullscreenDisplayMode(SDL_DisplayID displayID, int w, int h, float refresh_rate, SDL_bool include_high_density_modes, SDL_DisplayMode *mode);
 
 /**
  * Get information about the desktop's display mode.
@@ -604,7 +605,7 @@ extern SDL_DECLSPEC_TEMP const SDL_DisplayMode * SDLCALL SDL_GetClosestFullscree
  * \sa SDL_GetCurrentDisplayMode
  * \sa SDL_GetDisplays
  */
-extern SDL_DECLSPEC_TEMP const SDL_DisplayMode * SDLCALL SDL_GetDesktopDisplayMode(SDL_DisplayID displayID);
+extern SDL_DECLSPEC const SDL_DisplayMode * SDLCALL SDL_GetDesktopDisplayMode(SDL_DisplayID displayID);
 
 /**
  * Get information about the current display mode.
@@ -623,7 +624,7 @@ extern SDL_DECLSPEC_TEMP const SDL_DisplayMode * SDLCALL SDL_GetDesktopDisplayMo
  * \sa SDL_GetDesktopDisplayMode
  * \sa SDL_GetDisplays
  */
-extern SDL_DECLSPEC_TEMP const SDL_DisplayMode * SDLCALL SDL_GetCurrentDisplayMode(SDL_DisplayID displayID);
+extern SDL_DECLSPEC const SDL_DisplayMode * SDLCALL SDL_GetCurrentDisplayMode(SDL_DisplayID displayID);
 
 /**
  * Get the display containing a point.
@@ -753,7 +754,7 @@ extern SDL_DECLSPEC int SDLCALL SDL_SetWindowFullscreenMode(SDL_Window *window,
  * \sa SDL_SetWindowFullscreenMode
  * \sa SDL_SetWindowFullscreen
  */
-extern SDL_DECLSPEC_TEMP const SDL_DisplayMode * SDLCALL SDL_GetWindowFullscreenMode(SDL_Window *window);
+extern SDL_DECLSPEC const SDL_DisplayMode * SDLCALL SDL_GetWindowFullscreenMode(SDL_Window *window);
 
 /**
  * Get the raw ICC profile data for the screen the window is currently on.
@@ -761,11 +762,11 @@ extern SDL_DECLSPEC_TEMP const SDL_DisplayMode * SDLCALL SDL_GetWindowFullscreen
  * \param window the window to query.
  * \param size the size of the ICC profile.
  * \returns the raw ICC profile data on success or NULL on failure; call
- *          SDL_GetError() for more information.
+ *          SDL_GetError() for more information. This should be freed with SDL_free() when it is no longer needed.
  *
  * \since This function is available since SDL 3.0.0.
  */
-extern SDL_DECLSPEC_TEMP const void * SDLCALL SDL_GetWindowICCProfile(SDL_Window *window, size_t *size);
+extern SDL_DECLSPEC_FREE void * SDLCALL SDL_GetWindowICCProfile(SDL_Window *window, size_t *size);
 
 /**
  * Get the pixel format associated with the window.
@@ -785,11 +786,11 @@ extern SDL_DECLSPEC SDL_PixelFormat SDLCALL SDL_GetWindowPixelFormat(SDL_Window
  * \param count a pointer filled in with the number of windows returned, may
  *              be NULL.
  * \returns a NULL terminated array of SDL_Window pointers or NULL on failure;
- *          call SDL_GetError() for more information.
+ *          call SDL_GetError() for more information. This is a single allocation that should be freed with SDL_free() when it is no longer needed.
  *
  * \since This function is available since SDL 3.0.0.
  */
-extern SDL_DECLSPEC_TEMP SDL_Window * const * SDLCALL SDL_GetWindows(int *count);
+extern SDL_DECLSPEC_FREE SDL_Window ** SDLCALL SDL_GetWindows(int *count);
 
 /**
  * Create a window with the specified dimensions and flags.
@@ -1322,7 +1323,7 @@ extern SDL_DECLSPEC int SDLCALL SDL_SetWindowTitle(SDL_Window *window, const cha
  *
  * \sa SDL_SetWindowTitle
  */
-extern SDL_DECLSPEC_TEMP const char * SDLCALL SDL_GetWindowTitle(SDL_Window *window);
+extern SDL_DECLSPEC const char * SDLCALL SDL_GetWindowTitle(SDL_Window *window);
 
 /**
  * Set the icon for a window.