Fix confusing exception in ActiveSupport delegation
Have Postgres OID types inherit from general types

Using general types where possible. Several more can go away once
infinity gets figured out.
fix multiple hash preloads.  Fixes #14994
Merge pull request #15201 from sgrif/sg-types-postgresql

Have Postgres OID types inherit from general types
make the each visitor top-down left-right
prepopulate the dispatch cache so we don't need the ThreadSafe cache.
Merge pull request #15187 from v-yarotsky/fix_confusing_delegation_exception

Fix confusing exception in ActiveSupport delegation