Style: Enforce braces around if blocks and loops

Using clang-tidy's `readability-braces-around-statements`.
https://clang.llvm.org/extra/clang-tidy/checks/readability-braces-around-statements.html

servers/rendering/shader_language.h

@@ -770,8 +770,9 @@ private:
 	}
 
 	void _set_error(const String &p_str) {
-		if (error_set)
+		if (error_set) {
 			return;
+		}
 
 		error_line = tk_line;
 		error_set = true;