explicit versioning of nodeadm that should be used in EKS AMIs

[rpocase]

What would you like to be added:
Public nodeadm versioning of some kind. There are several options that can be left up to the implementation.

• releases within this repository (with a bundled version of nodeadm)
• split nodeadm its own repository, releases within the new repo

Why is this needed:
Its not clear how nodeadm is built and bundled into the public AMIs. Downstream consumers (e.g. [0]) cannot determine how to bundle nodeadm because its right source code to build against is not labeled. Initial searches point to platform9/nodeadm, which isn't the right version.

[0] - https://bugs.launchpad.net/cloud-images/+bug/2058610