Switch header convention from #include "SDL.h" to #include <SDL3/SDLh>

I ran this script in the include directory:
```sh
sed -i '' -e 's,#include "\(SDL.*\)",#include <SDL3/\1>,' *.h
```

I ran this script in the src directory:
```sh
for i in ../include/SDL3/SDL*.h
do hdr=$(basename $i)
   if [ x"$(echo $hdr | egrep 'SDL_main|SDL_name|SDL_test|SDL_syswm|SDL_opengl|SDL_egl|SDL_vulkan')" != x ]; then
        find . -type f -exec sed -i '' -e 's,#include "\('$hdr'\)",#include <SDL3/\1>,' {} \;
    else
        find . -type f -exec sed -i '' -e '/#include "'$hdr'"/d' {} \;
    fi
done
```

Fixes https://github.com/libsdl-org/SDL/issues/6575

src/power/SDL_power.c

@@ -19,7 +19,6 @@
   3. This notice may not be removed or altered from any source distribution.
 */
 #include "../SDL_internal.h"
-#include "SDL_power.h"
 #include "SDL_syspower.h"
 
 /*

src/power/SDL_syspower.h

@@ -25,7 +25,6 @@
 #ifndef SDL_syspower_h_
 #define SDL_syspower_h_
 
-#include "SDL_power.h"
 
 /* Not all of these are available in a given build. Use #ifdefs, etc. */
 SDL_bool SDL_GetPowerInfo_Linux_org_freedesktop_upower(SDL_PowerState *, int *, int *);

src/power/android/SDL_syspower.c

@@ -23,7 +23,6 @@
 #ifndef SDL_POWER_DISABLED
 #if SDL_POWER_ANDROID
 
-#include "SDL_power.h"
 #include "../SDL_syspower.h"
 
 #include "../../core/android/SDL_android.h"

src/power/emscripten/SDL_syspower.c

@@ -25,7 +25,6 @@
 
 #include <emscripten/html5.h>
 
-#include "SDL_power.h"
 
 SDL_bool
 SDL_GetPowerInfo_Emscripten(SDL_PowerState *state, int *seconds, int *percent)

src/power/haiku/SDL_syspower.c

@@ -40,7 +40,6 @@
 #define APM_DEVICE_ALL 1
 #define APM_BIOS_CALL (B_DEVICE_OP_CODES_END + 3)
 
-#include "SDL_power.h"
 
 SDL_bool
 SDL_GetPowerInfo_Haiku(SDL_PowerState * state, int *seconds, int *percent)

src/power/linux/SDL_syspower.c

@@ -31,7 +31,6 @@
 #include <dirent.h>
 #include <fcntl.h>
 
-#include "SDL_power.h"
 #include "../SDL_syspower.h"
 
 #include "../../core/linux/SDL_dbus.h"

src/power/macos/SDL_syspower.c

@@ -27,7 +27,6 @@
 #include <IOKit/ps/IOPowerSources.h>
 #include <IOKit/ps/IOPSKeys.h>
 
-#include "SDL_power.h"
 
 /* CoreFoundation is so verbose... */
 #define STRMATCH(a,b) (CFStringCompare(a, b, 0) == kCFCompareEqualTo)

src/power/n3ds/SDL_syspower.c

@@ -25,8 +25,6 @@
 
 #include <3ds.h>
 
-#include "SDL_error.h"
-#include "SDL_power.h"
 
 SDL_FORCE_INLINE SDL_PowerState GetPowerState(void);
 SDL_FORCE_INLINE int ReadStateFromPTMU(bool *is_plugged, u8 *is_charging);

src/power/psp/SDL_syspower.c

@@ -24,7 +24,6 @@
 #ifndef SDL_POWER_DISABLED
 #if SDL_POWER_PSP
 
-#include "SDL_power.h"
 #include <psppower.h>
 
 

src/power/uikit/SDL_syspower.h

@@ -22,7 +22,6 @@
 
 #if SDL_POWER_UIKIT
 
-#include "SDL_power.h"
 
 void SDL_UIKit_UpdateBatteryMonitoring(void);
 SDL_bool SDL_GetPowerInfo_UIKit(SDL_PowerState * state, int *seconds, int *percent);

src/power/uikit/SDL_syspower.m

@@ -25,8 +25,6 @@
 
 #import <UIKit/UIKit.h>
 
-#include "SDL_power.h"
-#include "SDL_timer.h"
 #include "SDL_syspower.h"
 
 #if !TARGET_OS_TV

src/power/vita/SDL_syspower.c

@@ -24,7 +24,6 @@
 #ifndef SDL_POWER_DISABLED
 #if SDL_POWER_VITA
 
-#include "SDL_power.h"
 #include <psp2/power.h>
 
 

src/power/windows/SDL_syspower.c

@@ -25,7 +25,6 @@
 
 #include "../../core/windows/SDL_windows.h"
 
-#include "SDL_power.h"
 
 SDL_bool
 SDL_GetPowerInfo_Windows(SDL_PowerState * state, int *seconds, int *percent)

src/power/winrt/SDL_syspower.cpp

@@ -23,7 +23,6 @@
 #ifndef SDL_POWER_DISABLED
 #if SDL_POWER_WINRT
 
-#include "SDL_power.h"
 
 extern "C"
 SDL_bool