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
Addresses [[ https://linear.app/comm/issue/ENG-5634/include-voiced-permission-blob-for-announcement-channels | ENG-5634 ]]
Depends on D9901