Set up a way for repos in PL orgs to easily use GitHub Actions cache on S3

[galargh]

We could use something like https://github.com/marketplace/actions/s3-cache-for-github-actions in the workflows. It'll probably need some tweaks though. To be evaluated if it's easier to contribute or build one from scratch.

We should use OIDC to verify where the requests are coming from https://docs.github.com/en/actions/deployment/security-hardening-your-deployments/configuring-openid-connect-in-amazon-web-services.

[galargh]

This is to work around the 10 GB GitHub Actions cache size limit. It's especially troublesome for Rust repos: https://filecoinproject.slack.com/archives/C03K82MU486/p1669016058704329