Update for SDL3 coding style (#6717)

I updated .clang-format and ran clang-format 14 over the src and test directories to standardize the code base.

In general I let clang-format have it's way, and added markup to prevent formatting of code that would break or be completely unreadable if formatted.

The script I ran for the src directory is added as build-scripts/clang-format-src.sh

This fixes:
#6592
#6593
#6594

test/testlocale.c

@@ -60,7 +60,7 @@ int main(int argc, char **argv)
         SDL_Quit();
     }
 
-   return 0;
+    return 0;
 }
 
 /* vi: set ts=4 sw=4 expandtab: */