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.

Fixes: #9832
Change-Id: I32b55de8625ec435edf916a91e65f61fda50cd51