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.
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Depends on D7069
Linear Task: https://linear.app/comm/issue/ENG-3305/avatars-feature-flag-service