⚡ find tests that can be unforked

[joerunde]

Description

This is a little sidequest inspired by @toddllm to make our tests run faster in CI. This PR marks tests by the type of cache that they use, and whether or not forking is strictly required for them.

This allows us to run tests that use the same type of vllm model cache without --forked, which saves a huge amount of time skipping spyre warmup for tests that hit the model cache.

Related Issues

Test Plan

As-is this doesn't change any behavior as the marking is strictly additive and none of these marks are used by our CI jobs currently.

We'll need to sync this with changes to the CI jobs to ensure that removing --forked for these cases actually works. I've manually verified that I can run both:

pytest tests -m "uses_llm and spyre and not fork_required"
pytest tests -m "uses_server and spyre and not fork_required"

on this branch without failure.

Checklist

• I have read the contributing guidelines
• My code follows the project's code style (run bash format.sh)
• I have added tests for my changes (if applicable)
• I have updated the documentation (if applicable)
• My commits include a Signed-off-by: line (DCO compliance)

[github-actions]

👋 Hi! Thank you for contributing to vLLM support on Spyre.
Just a reminder: Make sure that your code passes all the linting checks, otherwise your PR won't be able to be merged. To do so, run ./format.sh.
Now you are good to go 🚀.

We also recommend installing prek and configuring it to check your code before every local commit.

[maxdebayser]

typo: relelasing -> releasing

[maxdebayser]

LGTM