Treat __aenter__, __aexit__, and __anext__ as awaitable protocol
methods for unspecced mock() objects when configured via
when(...).thenReturn/thenRaise/thenAnswer flows.

Centralize awaitable detection in Mock.method_expects_awaitable().
Reuse it for method replacement coroutine marking, and update
StubbedInvocation to use the shared logic.

Add focused regression tests in tests/async_protocol_methods_test.py,
including functional async with and async for scenarios, plus
awaitable checks for __aenter__/__aexit__ and __anext__.

Include AtMost in verification_has_lower_bound_of_zero() so explicit
zero-match verification with atmost=n marks matching stubs as
intentionally checked.

This aligns bookkeeping with existing verification semantics where
atmost already allows zero matches, and fixes follow-up
verifyStubbedInvocationsAreUsed/InOrder zero-lower-bound flows.

Add focused tests showing that typing.Protocol works as a spec for
method existence checks, async/sync method behavior, and signature
validation, including inherited override signatures.

Create internal chain mocks in strict mode so unexpected/unconfigured
chain segments fail early with InvocationError instead of returning
None and crashing later with AttributeError.

Add regression coverage in chaining_test.py that asserts the exact
error message for mismatched chain segment arguments.

Partially reverts 8f13528 ("Fix dummy
single-stub rollback with registry unstub_mock")

In the test for the patch, we can clearly see that `dog` is still in
the scope of the function, so we cannot unregister it which would break
its tie its theMock.

In fact expecting `ArgumentError` is wrong for the non-strict mock. For
`verify` we raise a `VerificationError`, and ensure that by testing
before and after the failing configuration try.

This reverts commit ba08077.