Add support for additional test infrastructure providers

[evankanderson]

e.g. Equinix, AWS, etc.

Adding this to the roadmap, but it will definitely need some longer-term design and discussion with the CNCF test infrastructure community to make sure that we're building on supported foundations. (kubetest2? boskos?).

There's no urgent need for this; this is a tracking issue in case we discover that we either want broader k8s coverage or better stability / performance / cost in the future. (i.e. @dprotaso is currently tracking down upgrade test failures on GKE 1.21 that aren't present on GKE 1.20, and it would be interesting to see if the same errors are present on other clouds / infrastructure.)

[chizhg]

/cc @kvmware

[github-actions]

This issue is stale because it has been open for 90 days with no
activity. It will automatically close after 30 more days of
inactivity. Reopen the issue with /reopen. Mark the issue as
fresh by adding the comment /remove-lifecycle stale.

[chizhg]

/remove-lifecycle stale