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/rendering/rasterizer_rd/light_cluster_builder.cpp

@@ -203,6 +203,7 @@ void LightClusterBuilder::setup(uint32_t p_width, uint32_t p_height, uint32_t p_
 RID LightClusterBuilder::get_cluster_texture() const {
 	return cluster_texture;
 }
+
 RID LightClusterBuilder::get_cluster_indices_buffer() const {
 	return items_buffer;
 }
@@ -226,6 +227,7 @@ LightClusterBuilder::LightClusterBuilder() {
 	items_buffer = RD::get_singleton()->storage_buffer_create(sizeof(uint32_t) * 1024);
 	item_max = 1024;
 }
+
 LightClusterBuilder::~LightClusterBuilder() {
 	if (cluster_data.size()) {
 		RD::get_singleton()->free(cluster_texture);