implement basic typing for lambda elements

implement basic typing for lambda elements

These weren't working at all, so fixed things up and
added a test suite.   Keeping things very basic with Any
returns etc. as having more specific return types
starts making it too cumbersome to write end-user code.

Corrected the type passed for "lambda statements" so that a plain lambda is
accepted by mypy, pyright, others without any errors about argument types.
Additionally implemented typing for more of the public API for lambda
statements and ensured :class:`.StatementLambdaElement` is part of the
:class:`.Executable` hierarchy so it's typed as accepted by
:meth:`_engine.Connection.execute`.

Fixes: #9120
Change-Id: Ia7fa34e5b6e43fba02c8f94ccc256f3a68a1f445