Implement an admission webhook for `Catalog` resources

[everettraven]

If we continue with the approach introduced by operator-framework/catalogd#65 , we should introduce an admission webhook for Catalog resources as mentioned in operator-framework/catalogd#65 (comment) to ensure Catalog resources are meeting the proper requirements for reconciliation.

[ncdc]

We should first look to see if we can do this with CEL before starting down the webhook path

[camilamacedo86]

@ncdc @everettraven

Is that still a requirement?
Or we can close this one as outdated?

[grokspawn]

As part of our API audits for v1.0 release I think we met/exceeded the intent of this by leveraging kubebuilder/CEL in our types.
I'll close this issue.