Remove is_resource_enabled and requires from tests.

[junkmd]

The requires and is_resource_enabled functions found in the tests were only meaningful when using the test command in setup.py.

Currently, unit tests can be executed by: unittest discover -v -s ./comtypes/test -t comtypes\test.

In most cases, requires and is_resource_enabled are effectively dead code.
Therefore, they will be removed here and replaced with the standard skipping mechanisms provided by unittest if necessary.

If displaying missing resources or handling complex skip conditions becomes necessary, we can consider introducing unittest plugins or adopting pytest. IMO, such measures would be excessive at this stage.

The removal of these function definitions from test/__init__.py would also affect setup.py, so those changes are not included in the scope of this PR.