Some test suites have own test runners based on pytest, and they
don't need all stuff we use for test.py. Move all code related to
test.py framework to test/pylib/runner.py and use it as a plugin
conditionally (by using TEST_RUNNER variable.)
There is the fixture in `test/cql/conftest.py` which checks
CQL connection after each test and exit from pytest session if
the connection was failed. For CQL tests it's simply no
difference what to use: pytest.exit() or pytest.fail() because
tests are executing one-by-one in separate pytest sessions.
Change it to pytest.fail() for future integration into a single
pytest session.
Create a custom pytest test collector for .cql files and
move CQL test execution logic from `CQLApprovalTest` class
and `pylib/cql_repl/cql_repl.py` file to `CqlTest.runtest()`
method.
In result, the only difference between CQLApproval and Python
suite types is suffixes of test files.
