refine in_() check to use proper duck-typing for __clause_element__

refine in_() check to use proper duck-typing for __clause_element__

Fixed regression caused by an internal code change in response to recent
Mypy releases that caused the very unusual case of a list of ORM-mapped
attribute expressions passed to :meth:`.ColumnOperators.in_` to no longer
be accepted.

in this commit we had to revisit d8dd28c42e where mypy typing
didn't accept ColumnOperartors.   the type here is the _HasClauseElement[_T]
protocol which means we need to use a duck type for a runtime check.

Fixes: #12019
Change-Id: Ib378e9cb8defb49d5ac4d726ec93d6bdc581b6a9