[Enhancement] 1.16 documentation updates

[realshuting]

Description

This is the tracking issue for all doc updates for Kyverno 1.16 release:

• [ ] Fine-grained CEL policy exceptions: https://github.com/kyverno/kyverno/pull/14175
• [ ] Namespaced policies: vpol, dpol
• [x] Add metrics for CEL policies
• [ ] Add v1beta1 version for CEL policies
• [ ] Compatible matrix for CEL libs
• [x] reports exclusion via configurable label values

Slack discussion

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