Allow exit immediately functionality on runcmd list

[anmazzotti]

Currently all commands in a runcmd/commands list will be executed independently of each other.
If the first command fails, all the others will still be executed.

Note that this is also the cloud-init behavior, so this should count as a yip only feature request.

The request is to make this behavior toggable in yip. For example by adding stage options:

stages:
   my-stage:
     options:
       exitImmediately: true
     commands:
        - exit 2
        - echo "Success"

It would also be nice to enforce this value on all configs with an environment variable, so that it can be applied to cloud-init syntax configs as well.

This could help all those cases where a complex list of dependent commands needs to be executed, making the config itself more readable (instead of a giant pipe or an opaque bash script).

Could also help circumventing/mitigating issues like this one: rancher/cluster-api-provider-rke2#221

Still this would differ from cloud-init behavior, so it should be used with care.