[native] add feature flag to avatars render work

Summary:
added AVATARS_DISPLAY feature flag to all avatars render work that is ready to land. For this diff created a new hook called useShouldRenderAvatars which determines if the current user has the feature flag "on" and returns a boolean to either render or not render the avatar. The criteria for having the AVATARS_DISPLAY feature flag on is that they need to be a staff user. In subsequent diffs I will add the feature flag when introducing things like the thread avatars and user avatars in chat screen.

Depends on D7069

Linear Task: https://linear.app/comm/issue/ENG-3305/avatars-feature-flag-service

Test Plan:
Ginsu who is a staff user can see avatars, but Dan who is not a staff avatar can not see the rendered avatars on their screen:

Ginsu's screen:

Dan's screen:

Reviewers: ashoat, atul, tomek

Reviewed By: ashoat

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D7099