Rollup merge of rust-lang#154351 - nnethercote:overhaul-Erasable-impls, r=petrochenkov

Overhaul `Erasable` impls

This PR removes many unused `Erasable` impls, converts many of the hand-written impls to macro-generated impls, and sorts the macro's inputs. This cuts over 200 lines of code and fixes three FIXME comments.

r? @petrochenkov

Author: JonathanBrouwer