Add support for scaling non-eksctl created nodegroups

[aclevername]

Description

Add support for scaling non-eksctl created nodegroups #3079

Checklist

• Added tests that cover your change (if possible)
• Added/modified documentation as required (such as the README.md, or the userdocs directory)
• Manually tested
• Made sure the title of the PR is a good description that can go into the release notes
• (Core team) Added labels for change area (e.g. area/nodegroup) and kind (e.g. kind/improvement)

BONUS POINTS checklist: complete for good vibes and maybe prizes?! 🤯

• Backfilled missing tests for code in same general area 🎉
• Refactored something and made the world a better place 🌟

[aclevername]

./eksctl scale nodegroup --cluster jk --name ng-1 --nodes 3 --nodes-max 3
[ℹ]  scaling nodegroup "ng-1" in cluster jk
[ℹ]  waiting for scaling of nodegroup "ng-1" to complete
[ℹ]  waiting for scaling of nodegroup "ng-1" to complete
[ℹ]  nodegroup successfully scaled