Proposal: stop special casing constructors in collapse properties

CollapseProperties currently collapse properties on constructors unconditionally. This seems unnecessary with our type based optimizations (which will disambiguate properties on constructors when possible, if uncollapsed).

1) continue to collapse properties on constructors that are unescaped
2) enhance "RemoveUnusedClassProperties" or "RemoveUnusedPrototypeProperties" to be able to remove properties added to functions annotated as "constructors".