Add more tests

[ajschmidt8]

This PR includes the following changes:

• Uses os.makedirs to ensure that the output directories exist before writing the generated dependency files
• Adds more tests
  • These tests consume a dependencies.yaml file to produce some generated output files. The actual generated files are then compared against a set of expected files (which are committed in this PR) to ensure that the results are as expected. The generated files are also added to the .gitignore file.

[vyasr]

@ajschmidt8 I just got around to reviewing and realized you had merged! In any case everything looks good and I didn't have much to comment on here. The only recommendations I would make (not necessarily in scope for this PR) are:

• We should rename the main function in rapids_dependency_file_generator.py and reserve that for the CLI entrypoint in cli.py.
• We should start adding some documentation soon. Doesn't have to be fancy linted docstrings etc, just some basics for devs to get oriented when they first start looking through.

[ajschmidt8]

@ajschmidt8 I just got around to reviewing and realized you had merged! In any case everything looks good and I didn't have much to comment on here. The only recommendations I would make (not necessarily in scope for this PR) are:

• We should rename the main function in rapids_dependency_file_generator.py and reserve that for the CLI entrypoint in cli.py.
• We should start adding some documentation soon. Doesn't have to be fancy linted docstrings etc, just some basics for devs to get oriented when they first start looking through.

Sorry! Just trying to keep things moving since the GH Actions migrations depend on this work. I agree with both of these items.

For the second item, I would argue that we should have these docstrings linted. If RAPIDS is going to depend on this tool, we need to legitimize it as much as possible. I'm not super familiar with Python coding conventions, so if we can programmatically enforce best practices, I think that's a good idea.