CI: migrate self-hosted runners to GitHub-hosted and add pip caching

[liuxiaopai-ai]

Fixes #89

• Replace self-hosted runner labels (linux_x64/linux_arm64) with GitHub-hosted runners (ubuntu-latest / ubuntu-24.04-arm)
• Use actions/checkout@v4 (recursive submodules) instead of cloning into /tmp
• Add pip download caching for container-based jobs by pinning PIP_CACHE_DIR under ${{ github.workspace }}
• Improve concurrency group for push+PR events and add timeouts to bound CI runtime

Note: nightly_coverage still uses the existing Aliyun registry image. If that registry is not reachable from GitHub-hosted runners, a follow-up could move the image to GHCR/quay or rebuild the environment in-workflow.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[Cuiyus]

Thank you for your submission. As you rightly observed, the absence of efficient CI components—such as GitHub Actions runners and the checkout action—has significantly impaired the usability and maintainability of the zvec CI pipeline.

We are currently undertaking an internal integration of the CI system with GitHub Actions runners. During this effort, issue #128 was identified and documented. In parallel, we conducted a thorough review of the changes proposed in your pull request; several modifications enhancing workflow reliability and execution clarity.

However, considering that there are many issues with the zvec ci at present, we plan to initiate a PR specifically for the CI to conduct an initial optimization of zvec's ci. You can then add those meaningful changes on of this.

Once again, we would like to thank you for your attention to zvec. Your submission has enabled us to identify the deficiencies in the corresponding module.

[Cuiyus]

For linux x86/arm64 & mac arm64 & nightly_coverage, we have migrated to the GitHub-hosted runner. Please follow #171 for updates.

Currently, running zvec on the github-hosted runner(linux_x64) will result in an illegal instruction. We speculate that the "illegal instruction" that occurred in #101 might be caused by the fact that the std::string compare within the std::map set was enabled for vectorization. We are currently trying to fix it.

Therefore, cibuildwheel (for releasing zvec Python version) will not be modified for now.

We plan to fix this issue in version v0.3.0. You can also follow #101 where the subsequent relevant fix solutions will be updated.