Don't consider ShadowMethods reflectable (#67421)

Don't consider ShadowMethods reflectable (#67421)

Fixes #65612. This regression was exposed in #62891 - we had a mismatch between what methods are considered reflectable during scanning vs during optimized compilation due to extra array being injected for reflectable `params` methods on instantiated generic types.

There are two potential fixes - either expand the set of methods considered reflectable during scanning, or limit the number of methods considered reflectable in optimized compilation. It doesn't look like we need the expanded set, so going with a restriction instead. The CI may prove me otherwise, so keeping an open mind about this.