[web] Keyboard support for typeahead [3/13] - Renamed animation state

Summary: Renamed state that is used for animations only, so it's not confused with anything that might have to do with logic of displaying overlay.

Test Plan:
Typeahead without keyboard support works.
Final tests performed in last diffs.

Reviewers: inka, kamil, ginsu, tomek

Reviewed By: ginsu, tomek

Subscribers: ashoat, atul, tomek, ginsu, kamil, inka

Differential Revision: https://phab.comm.dev/D6043