[5/n] Native Typeahead - Add selection state to chat input bar

Summary:
Preparing for native typeahead.
Adding selection to state so we can control it in input bars. There was a problem on iOS desribed here: https://linear.app/comm/issue/ENG-2367#comment-8e0f3042.
It was solved by adding controlSelection flag. We set it to false initially so we don't control
selection. It will be set true when we want to manipulate selection when inserting usernames after tapping into typeahead buttons (incoming diffs)

Test Plan:
Checked if app builds.
Checked if text input works corretly (both Android and iOS)

Reviewers: inka, ginsu, kamil, michal, tomek, ashoat

Reviewed By: tomek, ashoat

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

Differential Revision: https://phab.comm.dev/D6367