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.

editor/progress_dialog.cpp

@@ -83,6 +83,7 @@ void BackgroundProgress::_task_step(const String &p_task, int p_step) {
 	else
 		t.progress->set_value(p_step);
 }
+
 void BackgroundProgress::_end_task(const String &p_task) {
 	_THREAD_SAFE_METHOD_
 
@@ -103,6 +104,7 @@ void BackgroundProgress::_bind_methods() {
 void BackgroundProgress::add_task(const String &p_task, const String &p_label, int p_steps) {
 	MessageQueue::get_singleton()->push_call(this, "_add_task", p_task, p_label, p_steps);
 }
+
 void BackgroundProgress::task_step(const String &p_task, int p_step) {
 	//this code is weird, but it prevents deadlock.
 	bool no_updates = true;