Auto merge of rust-lang#15484 - rmehri01:14779_bool_to_enum_assist, r=Veykril

feat: Bool to enum assist

This adds the `bool_to_enum` assist, which converts the type of boolean local variables, fields, constants and statics to a new `enum` type, making it easier to distinguish the meaning of `true` and `false` by renaming the variants.

Closes rust-lang#14779

Author: bors