Add support for Ignition v3

[johananl]

Allow CAPI users to leverage Ignition v3 when bootstrapping Flatcar nodes.

[vincepri]

Have we considered adopting butane config types in the bootstrap provider / machine resource in Cluster API?

[johananl]

I'd have to look at the specifics to have an informed opinion here. Care to elaborate @vincepri? 🙂

[johananl]

(I assume this is following this Slack thread but I'm not clear on the details.)

[vincepri]

Yep! Maybe let's sync up offline at some point and come up with a plan / CAEP 🙃

[johananl]

Relevant discussion: https://kubernetes.slack.com/archives/C8TSNPY4T/p1688643597808979

[johananl]

Upstream PR: kubernetes-sigs/cluster-api#9158