Make postgresql-query's `sqlExp` quasiquoter allow `#{}` embedding of `ToField` objects

[mzabani]

We currently alias it to hpgsql's sql quasi-quoter, which is not compatible to that extent, as it requires ToPgField instances for #{} embedding.

This may require making hpgsql's parser more flexible, or re-importing the existing implementation of the quasiquoter from postgresql-query and changing some bits.