Use astroid.MANAGER.ast_from_module_name instead of trying to manually
build the module object. Rename awesome_module.py to wildcard.py to
better reflect what's being tested, add empty.py and and do wildcard
import tests importing it.
Fixes incorrect module name passed in the test_wildcard_import_init unit
test, as well as removing a self import, both of which were introduced
at the creation of the test in 9c551b0.
One test that should fail with the current code, checking that there
will be no messages if the root is actually a package and __init__.py
and one test that passes, there is indeed a message 'wildcard-import'
when not an __init__.py file
