Add suffix-based matching for namespaces and excludedNamespaces

[jcstanaway]

Describe the solution you'd like

#1404 added prefix-based matching for namespaces & excludedNamespaces, but it would be useful to also enable suffix-based matching.

Our use case is to not enforce certain constraints in "*-dev" namespaces (our naming convention is to append the environment to namespaces). We've currently implemented this behavior within the constraint template rego code, but given the enhancement in #1404, it would seem to make sense to extend that to cover this use case.

not endswith(input.review.object.metadata.namespace, "-dev")

Anything else you would like to add:

Unclear if/how to handle user specifying wilds at both the beginning and end.
Maybe a more generic solution allowing a regex pattern should be supported?

Environment:
any

Gatekeeper version: future version
Kubernetes version: (use kubectl version): any supported by gatekeeper.

[jcstanaway]

Possibly a dupe of #1525.

[maxsmythe]

Definitely related to #1525

My biggest concern with more complex match criteria is that if we ever implement indexing to support large numbers of mutators or constraints, it may be harder to implement the index. Regex is for sure problematic. I think prefix/suffix may be less so?