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.

core/io/file_access_pack.cpp

@@ -224,12 +224,15 @@ void FileAccessPack::seek(size_t p_position) {
 	f->seek(pf.offset + p_position);
 	pos = p_position;
 }
+
 void FileAccessPack::seek_end(int64_t p_position) {
 	seek(pf.size + p_position);
 }
+
 size_t FileAccessPack::get_position() const {
 	return pos;
 }
+
 size_t FileAccessPack::get_len() const {
 	return pf.size;
 }
@@ -343,12 +346,15 @@ String DirAccessPack::get_next() {
 		return String();
 	}
 }
+
 bool DirAccessPack::current_is_dir() const {
 	return cdir;
 }
+
 bool DirAccessPack::current_is_hidden() const {
 	return false;
 }
+
 void DirAccessPack::list_dir_end() {
 	list_dirs.clear();
 	list_files.clear();
@@ -357,6 +363,7 @@ void DirAccessPack::list_dir_end() {
 int DirAccessPack::get_drive_count() {
 	return 0;
 }
+
 String DirAccessPack::get_drive(int p_drive) {
 	return "";
 }
@@ -440,6 +447,7 @@ Error DirAccessPack::make_dir(String p_dir) {
 Error DirAccessPack::rename(String p_from, String p_to) {
 	return ERR_UNAVAILABLE;
 }
+
 Error DirAccessPack::remove(String p_name) {
 	return ERR_UNAVAILABLE;
 }