[lib] Pull filterOutDisabledPermissions(permissionsBitmask) out of getCurrentUser

Summary:
We will need to use this logic at permission check sites (eg threadMemberHasPermission/threadHasPermission/etc). Eventually we'll consolidate so we use one hook for everything, but for now we're going to use this in a couple places so we can first remove usage from getCurrentUser.

Depends on D11741

Test Plan: This is a very simple extract/move diff. flow + careful reading + will be tested implicitly by later diffs in the stack.

Reviewers: ginsu, tomek, varun, will

Reviewed By: tomek

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D11742