setup JoinedDispatch to support pickling

setup JoinedDispatch to support pickling

Fixed issue where a :class:`.MetaData` collection would not be
serializable, if an :class:`.Enum` or :class:`.Boolean` datatype were
present which had been adapted. This specific scenario in turn could occur
when using the :class:`.Enum` or :class:`.Boolean` within ORM Annotated
Declarative form where type objects frequently get copied.

Fixes: #11365
Change-Id: Iaaa64baad79c41075d37cf53dade744d79e600a3
(cherry picked from commit 93cfb49572ac56bc320a09b82285bf8ef8cdff57)