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/variant_parser.cpp

@@ -42,6 +42,7 @@ CharType VariantParser::StreamFile::get_char() {
 bool VariantParser::StreamFile::is_utf8() const {
 	return true;
 }
+
 bool VariantParser::StreamFile::is_eof() const {
 	return f->eof_reached();
 }
@@ -62,6 +63,7 @@ CharType VariantParser::StreamString::get_char() {
 bool VariantParser::StreamString::is_utf8() const {
 	return false;
 }
+
 bool VariantParser::StreamString::is_eof() const {
 	return pos > s.length();
 }