This is to make room for `MemberInfoWithoutPermissions` or `MemberInfoSansPermissions, etc.
We're going to need both in different places in the codebase. Specifically we'll definitely need `MemberInfoWithPermissions` when constructing `RawThreadInfo`s for old clients, etc.
The goal at the end of the stack is for the client to only deal with `MemberInfoSansPermissions`.
Will try to make the changes as minimal as possible...
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Depends on D12295