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.

modules/gdscript/gdscript_function.cpp

@@ -1566,6 +1566,7 @@ Variant GDScriptFunction::call(GDScriptInstance *p_instance, const Variant **p_a
 const int *GDScriptFunction::get_code() const {
 	return _code_ptr;
 }
+
 int GDScriptFunction::get_code_size() const {
 	return _code_size;
 }
@@ -1583,6 +1584,7 @@ StringName GDScriptFunction::get_global_name(int p_idx) const {
 int GDScriptFunction::get_default_argument_count() const {
 	return _default_arg_count;
 }
+
 int GDScriptFunction::get_default_argument_addr(int p_idx) const {
 	ERR_FAIL_INDEX_V(p_idx, default_arguments.size(), -1);
 	return default_arguments[p_idx];