add RegistryEvents

add RegistryEvents

Added :class:`_orm.RegistryEvents` event class that allows event listeners
to be established on a :class:`_orm.registry` object. The new class
provides three events: :meth:`_orm.RegistryEvents.resolve_type_annotation`
which allows customization of type annotation resolution that can
supplement or replace the use of the
:paramref:`.registry.type_annotation_map` dictionary, including that it can
be helpful with custom resolution for complex types such as those of
:pep:`695`, as well as :meth:`_orm.RegistryEvents.before_configured` and
:meth:`_orm.RegistryEvents.after_configured`, which are registry-local
forms of the mapper-wide version of these hooks.

note this change was prematurely merged in 7111dc0cbaae and reverted
for re-review and additional changes.

Fixes: #9832
(cherry picked from commit 7111dc0cbaae2070173e9f4a054745ee7d036dfa)
Change-Id: I8d69f5c7e0d004f98b7449fefe87a03bb0f29e39