Validations - stop from making accidental deletions

[pawanpraka1]

We need a way to stop accidental "openebs" namespace or CR deletions. We need a webhook or OPA to validate the deletion request.

[RealHarshThakur]

@pawanpraka1 Would adding a finalizer work?

[pawanpraka1]

@RealHarshThakur that will not help here as CR will be marked for deletion which is what we want to avoid here.