[ci/build] Pin CI dependencies version with pip-compile

[khluu]

Due to recent CI failures related to new releases from CI dependencies, we should freeze all direct & underlying dependencies and update them periodically (once a week)

This PR moves all dependencies to requirements-test.in and generate requirements-test.txt using pip-compile with python 3.12 (same version being used on CI build). Also, transformers is pinned to 4.45.2 for now.
Next step is to configure GHA workflow (dependabot) to perform this pip compile once a week.

[github-actions]

👋 Hi! Thank you for contributing to the vLLM project.
Just a reminder: PRs would not trigger full CI run by default. Instead, it would only run fastcheck CI which starts running only a small and essential subset of CI tests to quickly catch errors. You can run other CI tests on top of those by going to your fastcheck build on Buildkite UI (linked in the PR checks section) and unblock them. If you do not have permission to unblock, ping simon-mo or khluu to add you in our Buildkite org.

Once the PR is approved and ready to go, your PR reviewer(s) can run CI to test the changes comprehensively before merging.

To run CI, PR reviewers can do one of these:

• Add ready label to the PR
• Enable auto-merge.

🚀

[khluu]

looks like requirements-test.txt is overriding requirements-common.txt, numpy is 2.0.2 even when requirements-common.txt limits it to < 2.0.0

[khluu]

Also pin torch==2.5.0 and numpy < 2.0.0 in requirements-test.in