[compiler] Kill markReactiveIdentifier and friends

Summary:
With the previous PR we no longer need to mark identifiers as reactive in contexts where we don't have places. We already deleted most uses of markReactiveId; the last case was to track identifiers through loadlocals etc -- but we already use a disjoint alias map that accounts for loadlocals when setting reactivity.

ghstack-source-id: 69ce0a78b0729da3fe9d08177bf7d827af5325fb
Pull Request resolved: https://github.com/facebook/react/pull/31178