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.

scene/gui/texture_button.cpp

@@ -270,14 +270,17 @@ void TextureButton::set_pressed_texture(const Ref<Texture2D> &p_pressed) {
 	pressed = p_pressed;
 	update();
 }
+
 void TextureButton::set_hover_texture(const Ref<Texture2D> &p_hover) {
 	hover = p_hover;
 	update();
 }
+
 void TextureButton::set_disabled_texture(const Ref<Texture2D> &p_disabled) {
 	disabled = p_disabled;
 	update();
 }
+
 void TextureButton::set_click_mask(const Ref<BitMap> &p_click_mask) {
 	click_mask = p_click_mask;
 	update();
@@ -286,15 +289,19 @@ void TextureButton::set_click_mask(const Ref<BitMap> &p_click_mask) {
 Ref<Texture2D> TextureButton::get_normal_texture() const {
 	return normal;
 }
+
 Ref<Texture2D> TextureButton::get_pressed_texture() const {
 	return pressed;
 }
+
 Ref<Texture2D> TextureButton::get_hover_texture() const {
 	return hover;
 }
+
 Ref<Texture2D> TextureButton::get_disabled_texture() const {
 	return disabled;
 }
+
 Ref<BitMap> TextureButton::get_click_mask() const {
 	return click_mask;
 }