solve github actions windows native-tls build

[clux]

Problems with the github actions ci setup from #562 (which ALMOST gets a working windows build!) is that openssl is either too slow to install, or it slows down all the other jobs.

Options considered:

• ❌ adding openssl vendored feature everywhere (but slows down linux builds between 30-80%)
• ❌ adding openssl vendored under a cfg.windows config (but this requires resolver2)
• ❌ switching to resolver2 (but this make every crate herein unbuildable with cargo build because we can't select an k8s-openapi feature as a dependency - see features2#drawbacks)
• ❌ adding a plain vcpkg install (but this adds 6minutes to the windows build (other cached actions are 3min vs. 9min on windows (even after disabling parts of the tests))
• ❓adding run-vcpkg caching action for a smarter openssl install (but we haven't made this work yet, and have not managed to fix yet (furthest result))
• ❓adding a native-tls-vendored feature and forking the matrix job to special-case invoke the vendored feature (a bit of work but is doable, some unknown w.r.t. what -vendored libraries to use, follow reqwest with native-tls/vendored?)

Stashing down this because we would like to solve windows CI, but in a time/cache-efficient setup so that we don't have these enormous cycles just because of it.

sketches

vcpkg caching sketch:

      - name: Windows vcpkg install openssl and cache
        uses: lukka/run-vcpkg@v6
        if: matrix.os == 'windows-latest'
        with:
          vcpkgArguments: 'openssl:x64-windows'
          vcpkgDirectory: '${{ runner.workspace }}/b/vcpkg'
          vcpkgGitCommitId: 'master'

with VCPKGRS_DYNAMIC: 1 evar, was the furthest the caching one got.