ENG-6388 split adhoc permission into sql and sqlread

So, having scanned the diff, I don't understand what happened here.  It looks like ADHOC, which used to be read/write, morphed (at least in places) into SQLREAD, which is read-only, and SQL, which is new, and claims to be an alias for ADHOC, is created.  Do we need SQL and ADHOC?  Is the existence of ADHOC just for backward-compatibility and the existence of SQL for naming-sanity?