use tmp_path_factory to build in the vars and not in the tests path

https://github.com/kjaymiller/render_engine_theme_kjaymiller/blob/3d1097811a85967e474eaa54586415b4e4245706/tests/conftest.py#L9-L27

In all the other render-engine projects the design is to use the [`tmp_path_factory`](https://docs.pytest.org/en/7.1.x/how-to/tmp_path.html#the-tmp-path-factory-fixture) to build a tmp directory and then use that in the tests.

This eliminates the potential to add the output folder from tests to the repo and it ensures that the build is new with each test run.

Start with tests/conftest.py lines 9-27 and compare the fixture setup with the linked pytest tmp_path_factory documentation. The work is done when builds use a temporary directory rather than the tests path and the test suite still passes with fresh output on each run.

Written by the indexing model from the issue text.