Create and use self developed TestBears for tests in tests/generation/Bears.py

Currently, some of the tests use the bears from actual `coala-bears` dependency. Since coala-quickstart has `dev` version of `coala-bears` as a dependency, upstream changes to the bears can cause the tests to fail (because a lot of filtering based on meta information like requirement version, CAN_DETECT capability, language, etc, is done in quickstart while selecting bears)

So instead of running tests on actual bears in coala-bears package, we should create our own TestBears and use them with ``TestUtilites.bear_test_module`` context. This will also speed up the testing time imo.

Start in tests/generation/Bears.py and inspect the tests that currently use bears from the coala-bears dependency. Use the TestUtilites.bear_test_module context with locally defined TestBears, then run the affected test module to confirm the tests no longer depend on upstream bear metadata or behavior.

Written by the indexing model from the issue text.