implement active_history for composites

implement active_history for composites

Fixed bug where the "active history" feature was not fully
implemented for composite attributes, making it impossible to receive
events that included the "old" value.   This seems to have been the case
with older SQLAlchemy versions as well, where "active_history" would
be propagated to the underlying column-based attributes, but an event
handler listening to the composite attribute itself would not be given
the "old" value being replaced, even if the composite() were set up
with active_history=True.

Additionally, fixed a regression that's local to 2.0 which disallowed
active_history on composite from being assigned to the impl with
``attr.impl.active_history=True``.

Fixes: #9460
Change-Id: I6d7752a01c8d3fd78de7a90de10e8c52f9b3cd4e