Propagate key for collection events

Propagate key for collection events

Added new parameter :paramref:`_orm.AttributeEvents.include_key`, which
will include the dictionary or list key for operations such as
``__setitem__()`` (e.g. ``obj[key] = value``) and ``__delitem__()`` (e.g.
``del obj[key]``), using a new keyword parameter "key" or "keys", depending
on event, e.g. :paramref:`_orm.AttributeEvents.append.key`,
:paramref:`_orm.AttributeEvents.bulk_replace.keys`. This allows event
handlers to take into account the key that was passed to the operation and
is of particular importance for dictionary operations working with
:class:`_orm.MappedCollection`.

Fixes: #8375
Change-Id: Icc472f7c28848f94e15c94a399cc13a88782e1e4