support ansible module

https://cloudinit.readthedocs.io/en/latest/reference/modules.html#ansible

In our case, we may not want to install ansible during boot as its a heavy operation, as we cant know if even python is on the image.

But, we could do:

• check if ansible is available
• check if git is available (if we are asking to pull a remote playbook)
• run ansible

If ansible is not there:

• check if pip is available in the system
• check if git is available (if we are asking to pull a remote playbook)
• install ansible via pip to a tmp dir
• run ansible from there

I think we could start small with the pluging and build on top of it.

something like

stages:
	boot:
		ansible:
			pull:
			    url: https://github.com/holmanb/vmboot.git
				    playbook_name: ubuntu.yml

as a start would be good

Start by reviewing the repository's boot-stage plugin architecture and how it processes the YAML example in the issue. Define the initial ansible plugin scope around detecting available tools, optionally fetching a remote playbook, and running the requested playbook; done means the sample configuration works without always installing ansible during boot.