Return given type when it matches the adaptation

Return given type when it matches the adaptation

The rules for type coercion between :class:`.Numeric`, :class:`.Integer`,
and date-related types now include additional logic that will attempt
to preserve the settings of the incoming type on the "resolved" type.
Currently the target for this is the ``asdecimal`` flag, so that
a math operation between :class:`.Numeric` or :class:`.Float` and
:class:`.Integer` will preserve the "asdecimal" flag as well as
if the type should be the :class:`.Float` subclass.

Change-Id: Idfaba17220d6db21ca1ca4dcb4c19834cd397817
Fixes: #4018