Add declarative validation linting to optionalorrequired

[JoelSpeed]

This PR updates the optionalorrequired linter to also understand the semantics of the +k8s:Optional and +k8s:Required markers.

In particular, it checks that both are not set at the same time, and, that if another optiona/required marker is present, that the semantics match.

CC @yongruilin

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: JoelSpeed

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [JoelSpeed]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[sivchari]

/lgtm

[JoelSpeed]

Oops, I probably should have held this

@yongruilin if you have any feedback, please review here and I'll create a follow up PR

[sivchari]

Oh no, sorry.
I considered it you started to handle validation-gen.

[JoelSpeed]

Don't worry! I've spoken with @yongruilin already and was intending to start supporting declarative validation so that we can cover the linting use case of that project as well.

I'm currently working on enabling kube-api-linter for kubernetes itself and this is one of the prerequisites, so I was intending to merge over the next few days anyway