Spinup spot instance for CI with cirun

[aktech]

This would first try to spinup spot instance and if that fails then will spinup on-demand instance.

To save CI costs this would first try to spinup spot instance first and if that fails then will spinup on-demand instance.
See https://docs.cirun.io/reference/fallback-runners#example-3-preemptiblenon-preemptible-instances

Reference Issues or PRs

What does this implement/fix?

Put a x in the boxes that apply

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds a feature)
• Breaking change (fix or feature that would cause existing features not to work as expected)
• Documentation Update
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Build related changes
• Other (please describe):

Testing

• Did you test the pull request locally?
• Did you add new tests?

Any other comments?

[costrouc]

LGTM. Thanks @aktech