Add PXE boot support to k3s_agent role

[l50]

Huge fan of this project, thanks for creating and maintaining it!

I'm happy to submit another PR to implement PXE boot support for the server role, but wanted to make sure there was interest in the existing work I've done first.

Proposed Changes

• Introduced enhancements to the k3s_agent role to address a specific issue encountered while setting up a Raspberry Pi 4 for PXE booting. This includes adding checks for PXE-boot conditions and modifying the k3s.service.j2 template to dynamically set the native snapshotter, resolving issues related to "overlayfs" snapshotter incompatibilities in such setups.
• Improved overall maintainability and readability of the k3s_agent role by adopting idiomatic Ansible practices. This involved restructuring tasks into logical blocks, implementing conditional task execution, and transitioning to Ansible builtin modules for future-proofing and better compatibility.

Context

While adding a new Raspberry Pi 4 to the cluster and setting it up to PXE boot from a Synology NAS, I encountered an error related to the "overlayfs" snapshotter. After some investigation, I realized that specifying the "native" snapshotter could resolve this. These changes are intended to help others who might face the same issue, streamlining their setup process and enhancing the usability of this project.

Checklist

• [x] Tested on two Raspberry Pi 4Bs: one configured to boot from an external SSD and the other set up for network booting (PXE) from a NAS.
• [x] Ran site.yml playbook
• [x] Ran reset.yml playbook
• [x] Did not add any unnecessary changes
• [x] Ran pre-commit install at least once before committing
• [x] 🚀

[timothystewart6]

Looks like there are conflicts that need to be resolved

[timothystewart6]

@l50 I've love to get this in if this is still valid. There are a few small conflicts with all the changes that need to be resolved first

[l50]

Apologies for the delay - conflict resolved.

[timothystewart6]

No worries at all and no rush! I just wanted to ping you just to be sure this is something you wanted to be included. My fault that the PRs got backed logged, but all caught up now that CI is working.

[l50]

Alright, finally had a minute to sit down and actually update everything. Hopefully this'll do it with the CI.

[timothystewart6]

Thank you!