Update Ecosystems Mock Test

[NeilMathew-git]

This PR adds two mock-based unit tests for the update_ecosystems method in osv_source.py to improve coverage without relying on external API calls or real gsutil interactions.

test_update_ecosystems_mocked:
Uses patch to mock out aio_run_command and simulate a basic case where a single ecosystem (ecosystem1) is listed and includes an all.zip file. Verifies that it's correctly recognized and stored.

test_update_ecosystems:
Tests the scenario where multiple ecosystems (python, rust) are listed, but only one (python) includes all.zip. Confirms that rust is excluded from the final result.

[terriko]

Heads up: it still looks like some of the test code is in the incorrect file.

[NeilMathew-git]

Sorry, I forgot to add one of the files when commiting. I just edited the PR on github directly, let me know if there is any other problem.

[terriko]

Still some rogue imports left in osv_source.py.

If you're not sure how to check what's in your PR on the command line, don't forget that you can click the "files changed" tab on github's web interface to see what you're submitting so you can fix it up without waiting for review!

[terriko]

I'm going to close this since it's been a month without action and I'm guessing you've moved on now that gsoc applications are done, but do feel free to re-open if you want to work on it later!