ci: a new prep-deps workflow with caching (#29979)

[danjm]

• prep-deps

• There's a new workflow that parallels the CircleCI workflow. prep-deps runs first and caches the result, then prep-build-test-webpack makes an artifact, then the benchmarks run.

• Several of the existing workflows were changed to now depend on prep-deps

• Many of the file changes are just using the new checkout-and-setup@caching and deleting the independent "Checkout repository" step

• vars.USE_CACHING No longer using this

• This allows us to toggle the caching feature on and off in a centralized way. I left instructions as a comment in main.yml for how to toggle it. We can discuss implementing this in a different way, but passing this variable through different workflows is actually kind of a pain (that's the first way I implemented it). Several of the jobs are 30-60 seconds faster when this is turned on.

• test-short-suite repository-health-checks

• I think this could be slightly controversial, but I think it's for the better.

• I noticed that there were 7 individual really short tests, that each ran on their own VM. Each VM instance took about 1m30s to execute. I combined these together into a single VM that runs all the short tests in sequence, and takes about 1m20s combined. The if: always() statements make all independent tests run, even if one fails.

• The 7 jobs were: test-lint-shellcheck, test-lint-changelog, test-lint-lockfile, test-deps-audit, test-yarn-dedupe, test-deps-depcheck, validate-lavamoat-allow-scripts

• If this were running on VMs that cost money, this would be a no-brainer. As is on GitHub runners, it doesn't really cost us any time or money. All we can really say is 7 separate jobs burn fossil fuels for a slight bit of convenience in terms of seeing individual test failures in the GitHub PR page.

• Depends on feat: GitHub-hosted runners for benchmarks #29955 MERGED

• Merge this caching branch of github-tools: ci: new checkout-and-setup to support prep-deps and caching github-tools#42 MERGED

• Change checkout-and-setup@caching and checkout-and-setup-secure@caching to new @hash

Split off from: #29955

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Description

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