Util: Forward declare where possible in format.h

src/util/format/format.h

@@ -12,12 +12,14 @@
 #include <string>
 #include <string_view>
 
-#include "util/format/builder.h"
+#include "util/format/formatter.h"
-#include "util/format/parser.h"
 #include "util/format/toformat.h"
 
 namespace Util::Format {
 
+class Builder;
+class Parser;
+
 struct Parameter {
 	const void* value;
 	void (*format)(Builder& builder, const void* value);