Feature: Ability to add server and worker k3s additional args

[mannp]

The ability to add k3s server and worker additional arguments allows more flexibility in the creation of the cluster.

"k3s_extra_server_args" -> Ref: https://rancher.com/docs/k3s/latest/en/installation/install-options/server-config/

"k3s_extra_worker_args" -> Ref: https://rancher.com/docs/k3s/latest/en/installation/install-options/agent-config/

Think I messed up in the previous PR, can separate the changes if they are agreeable :)

[mannp]

@fvumbaca I've made some changes, see what you think.