[cli] Enable job test command to use the --config-file option

[fallonchen]

klio job test currently takes in the --config-file option but does nothing with it, since the requires_config_file flag is set to False.

The config file option was also ignored in klio-exec, but that was fixed via PR 177.

This PR sets enables the use of the --config-file option by doing 2 things:

1. Setting TestPipeline().requires_config_file to True.
2. This PR also adjusts the way TestPipeline handles command generation so that the --config-file option is appended after the test command, but before pytest arguments are added.

Before this change, the generated command would be:

klio job test -- py_arg1 pyarg2 ... pyargN --config-file config.yaml

This causes the --config-file option to be ignored.

After this change, the generated command would be:

klio job test --config-file config.yaml -- py_arg1 pyarg 2 .. pyargN

Checklist for PR author(s)

• Format the pull request title like [cli] Fixes bugs in 'klio job fake-cmd'.
• Changes are covered by unit tests (no major decrease in code coverage %) and/or integration tests.
• Document any relevant additions/changes in the appropriate spot in docs/src.
• For any change that affects users, update the package's changelog in docs/src/reference/<package>/changelog.rst.

[DanSimon]

👍