Reader-only refactoring rules

[jackfirth]

Some refactoring rules, especially those for small #lang-based DSLs like #lang resyntax/test, don't actually need the source code to be expanded and fully analyzed. There should be a way for refactoring rules to restrict themselves to "reader-only" behavior. If all rules in the refactoring suite for a source are reader-only, Resyntax should skip the expansion and analysis phases of its pipeline.