Ignore ephemeral classes in test_all_present()

Ignore ephemeral classes in test_all_present()

Fixed a regression in the test suite where the test called
``CompareAndCopyTest::test_all_present`` would fail on some platforms due
to additional testing artifacts being detected. Pull request courtesy Nils
Philippsen.

In some circumstances, ephemeral class objects that are created within
the scope of a test method don't seem to be garbage collected directly
on exit. Filter out classes created in test modules.

Fixes: #7450
Closes: #7451
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/7451
Pull-request-sha: 135a8aaba2c6941460c7f45aa1a55c8f6b9eb43d

Change-Id: I621967bd916089dc1e3f98625fd2a852cd9fd712