Revert AppenderQuery modifications from ORM

Revert AppenderQuery modifications from ORM

We are unfortunately stuck with this class completely
until we get rid of "dynamic" altogether.    The usage
contract includes the "query_class" mixin feature where
users add their own methods, and this use case  very
well in line with 2.0's contract.  As Query is not going away
in any case this has to stay in "legacy" style, there's no
point trying to change it as the new version was still fully
dependent on Query.

Fixes: #5981
Change-Id: I1bc623b17d976b4bb417ab623248d4ac227db74d