Refactor some testing fixtures

[derek-globus]

What?

1. Updated CLI Invoke path to be less verbose.
   • Was: result = cli_runner.invoke(globus_registered_api.cli.cli, ["api", "list"])
   • Now is: result = gra(["api", "list"])
2. Updated flows response url patterns to be distributed by fixture

Why?

1. Remove boiler invocations characters. Shortening 49 characters -> 4 meant that a lot of invocations which previously needed to be splatted out across a number of lines could be consolidated to a single line. This helps with legibility in my opinion (reading commands horizontally instead of vertically).
2. Move away from importing from conftest models dependencies in a more pytest-y way.
   • Notably these imports broke once I added a child conftest.py under tests/commands/conftest.py.

Note

This PR is definitely opinionated.
I think it improves the test suite readability but fully acknowledge that's pretty subjective. Even more than normal, happy to discuss or hear dissenting opinions if folks disagree.