[Tech Debt] Update config. vars in Pytest fixtures

[seanpreston]

Throughout our test suite there are many areas where we update config. vars within a test.

config.execution.MASKING_STRICT = ...

This isn't ideal because if the test halts mid-execution, the value is never reset and could cause cascade failures into other tests. A better solution is to use a pytest fixture:

@pytest.fixture
def with_strict_masking():
    config.execution.MASKING_STRICT = False
    yield
    config.execution.MASKING_STRICT = True

as these will clean-up after themselves if the test fails.

Another option is to override pytest.ini vars directly.