feat: add tests for dependency / package management

[jakelorocco]

Misc PR

Type of PR

• Bug Fix
• New Feature
• Documentation
• Other

Description

• Link to Issue: Fixes N/A

Adds a series of tests to address issues we had previously seen with imports / dependencies. The tests:

• ensure that only packages associated with a dependency group (like hf / litellm) are imported by their relevant module / file
• ensure that new dependency groups get new tests added
• ensure that Mellea import time doesn't grow beyond 750ms (we can refine this number, but I'm unsure how stable it is on github action runners)

Testing

• Tests added to the respective file if code was changed
• New code has 100% coverage if code as added
• Ensure existing tests and github automation passes (a maintainer will kick off the github automation when the rest of the PR is populated)

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