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 RawThreadInfos 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...
Depends on D12295