feat: add spot instances

[llinros]

Adds option to use spot instances
fixes #259

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[comment-bot-dev]

@llinros
Thanks for the PR! 🚀
✅ Lint checks have passed.

[github-actions]

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[fabianrenner]

When is this expected to be merged?

[abatilo]

@apeabody or @g-awmalik maybe? Could we get someone to take a look at these changes and re-open this PR?

[apeabody]

/gcbrun

[karolcienkosz]

Hi, is there any chance for review?

[apeabody]

/gcbrun

[apeabody]

Thanks for the contribution @llinros! - This looks good from a code review stand point. Ideally we should have an test exercise spot=true.

[bharathkkb]

/gcbrun

[g-awmalik]

/gcbrun