[ci] Skip Playwright system deps install on subsequent self-hosted runs (#92893)
## What
Use a stamp file to skip `playwright install --with-deps` after the
first successful run on a self-hosted runner.
## Why
`--with-deps` runs `sudo apt-get install` for Playwright's system
dependencies every time, even when they're already installed. On
self-hosted runners this takes ~10s of no-op `apt-get` checking. After
the first install, subsequent runs only need `playwright install` (which
downloads browser binaries if the version changed, and is instant when
cached).
The assumption is that on most of the runners, `playwright` will be the
same version on each, and the deps that are installed are compatible
within each version.
Most of the time this step is ~3s, when everything is healthy and
up-to-date.
Occasionally these steps will hiccup on builds when we're already really
got these deps installed so this chops a little bit off each one. This
also helps when APT mirrors go down.
## How
- First run: `playwright install --with-deps` + write
`~/.cache/playwright-deps-installed`
- Subsequent runs: stamp file exists, run `playwright install` without
`--with-deps`
- The stamp persists on self-hosted runners across jobs
- Fresh/reimaged runners don't have the stamp, so they get the full
install
- The cache is ignored if the most recently installed playwright version
doesn't match
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