For both COMMUNITY_OPEN_ANNOUNCEMENT_SUBTHREAD and COMMUNITY_SECRET_ANNOUNCEMENT_SUBTHREAD, we should include a Voiced permission blob. This should just be a union between the existing thread permissions blob and the voiced permissions blob. This is in an effort to correctly have the 'Voiced in announcement channels' user-surfaced permission allow users to speak in announcement channels.
Will add @ashoat as a reviewer for some diffs here since this is a solution we discussed in our 1:1
Depends on D9901