Style: Enforce separation line between function definitions

I couldn't find a tool that enforces it, so I went the manual route:
```
find -name "thirdparty" -prune \
  -o -name "*.cpp" -o -name "*.h" -o -name "*.m" -o -name "*.mm" \
  -o -name "*.glsl" > files
perl -0777 -pi -e 's/\n}\n([^#])/\n}\n\n\1/g' $(cat files)
misc/scripts/fix_style.sh -c
```

This adds a newline after all `}` on the first column, unless they
are followed by `#` (typically `#endif`). This leads to having lots
of places with two lines between function/class definitions, but
clang-format then fixes it as we enforce max one line of separation.

This doesn't fix potential occurrences of function definitions which
are indented (e.g. for a helper class defined in a .cpp), but it's
better than nothing. Also can't be made to run easily on CI/hooks so
we'll have to be careful with new code.

Part of #33027.

servers/audio/audio_stream.cpp

@@ -312,6 +312,7 @@ void AudioStreamPlaybackRandomPitch::stop() {
 		;
 	}
 }
+
 bool AudioStreamPlaybackRandomPitch::is_playing() const {
 	if (playing.is_valid()) {
 		return playing->is_playing();
@@ -335,6 +336,7 @@ float AudioStreamPlaybackRandomPitch::get_playback_position() const {
 
 	return 0;
 }
+
 void AudioStreamPlaybackRandomPitch::seek(float p_time) {
 	if (playing.is_valid()) {
 		playing->seek(p_time);