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/plugins/asset_library_editor_plugin.cpp

@@ -72,6 +72,7 @@ void EditorAssetLibraryItem::_asset_clicked() {
 void EditorAssetLibraryItem::_category_clicked() {
 	emit_signal("category_selected", category_id);
 }
+
 void EditorAssetLibraryItem::_author_clicked() {
 	emit_signal("author_selected", author_id);
 }
@@ -297,6 +298,7 @@ EditorAssetLibraryItemDescription::EditorAssetLibraryItemDescription() {
 	get_ok()->set_text(TTR("Download"));
 	get_cancel()->set_text(TTR("Close"));
 }
+
 ///////////////////////////////////////////////////////////////////////////////////
 
 void EditorAssetLibraryItemDownload::_http_download_completed(int p_status, int p_code, const PackedStringArray &headers, const PackedByteArray &p_data) {
@@ -437,6 +439,7 @@ void EditorAssetLibraryItemDownload::_notification(int p_what) {
 		} break;
 	}
 }
+
 void EditorAssetLibraryItemDownload::_close() {
 	// Clean up downloaded file.
 	DirAccess::remove_file_or_error(download->get_download_file());
@@ -650,6 +653,7 @@ void EditorAssetLibrary::_select_category(int p_id) {
 		}
 	}
 }
+
 void EditorAssetLibrary::_select_asset(int p_id) {
 	_api_request("asset/" + itos(p_id), REQUESTING_ASSET);
 }