`getUniversalCommunityRootPermissionsBlob` is going to emulate the way we construct permissions blobs so it's more extendible towards separating permissions included for all roles in both `COMMUNITY_ROOT` and `COMMUNITY_ANNOUNCEMENT_ROOT`.
I'm not completetly deleting `universalCommunityPermissions` in `thread-permissions-types.js` yet, but I will do that once I land this entire stack + rebase the stack starting at D9493, since otherwise it'll cause a ton of merge conflicts and broken unit tests.
The rest of this stack will update usages of `universalCommunityPermissions` besides the unit test with this new method.
Addressess [[ https://linear.app/comm/issue/ENG-5761/refactor-thread-permissions-code | ENG-5761 ]]