Update validation failure prompts and document "auto approve" variable

[aarnq]

Description

To smooth out the contributor experience we should improve the way prompts are handled in the cli, and give some exposure that one can set CK8S_AUTO_APPROVE during contribution only to skip them.

Additional context

One problem is that the config validation basically runs on two or three levels, so for each apply, and if you broke the config during contribution, then you have to accept the prompts to continue.

These errors should really only cause one prompt.

Additionally all prompts should have the same question, either do you want to continue, or do you want to abort, not mix them.

Definition of done

• [ ] Single prompt type, either continue or abort.
• [ ] Single prompt for groups of failure
• [ ] Contributor guide addition to auto approve prompt.

[simonklb]

When documenting CK8S_AUTO_APPROVE it's important that it says that this also automatically answers yes to everything else as well (e.g. helmfile apply) not just the config validation.