Cache e2e image builds

[alexander-demicev]

What this PR does / why we need it:

Cache e2e image builds

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Special notes for your reviewer:

Checklist:

• squashed commits into logical changes
• includes documentation
• adds unit tests
• adds or updates e2e tests

[salasberryfin]

Thanks for this @alexander-demicev. Perhaps this may also help with adding RKE2 scenarios to short tests.

[salasberryfin]

I'm now seeing some authentication errors when it tries to push the cache data to ghcr registry:

ERROR: error writing layer blob: unexpected status from POST request to https://ghcr.io/v2/rancher/turtles-e2e-cache/blobs/uploads/: 403 Forbidden

[furkatgofurov7]

I'm now seeing some authentication errors when it tries to push the cache data to ghcr registry:

ERROR: error writing layer blob: unexpected status from POST request to https://ghcr.io/v2/rancher/turtles-e2e-cache/blobs/uploads/: 403 Forbidden

Yes, I also noticed it in the e2e tests here

[alexander-demicev]

@salasberryfin @furkatgofurov7 github uses my account crendentials to push cache to GCHR registry when running tests from the PR, I changed that to only push cache for nightly builds

Changed it to use github/cache action so we can use cache in any PR or E2E run

[salasberryfin]

Thanks, I think it's nice that we can run it on PRs also.