feat: allow for more customizations for k3s installs

[dgershman]

Description

This would allow for more flexibility in creating a k3s installation; for example setting up a 2nd agent node.

Related Issue

Relates to #2243

Checklist before merging

• Test, docs, adr added or updated as needed
• Contributor Guide Steps followed

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

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  Coverage        ?   26.62%           
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  Files           ?       89           
  Lines           ?     6715           
  Branches        ?        0           
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  Hits            ?     1788           
  Misses          ?     4720           
  Partials        ?      207           

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[lucasrod16]

Hey @dgershman,

I left some comments on #2243. It would be great to finalize and merge the ADR before starting the implementation.

Thanks!