Automatic merge from submit-queue (batch tested with PRs 46620, 46732, 46773, 46772, 46725)

Instrument advanced auditing

Add prometheus metrics for audit logging, including:

- A total count of audit events generated and sent to the output backend
- A count of audit events that failed to be audited due to an error (per backend)
- A count of request audit levels (1 per request)

For https://github.com/kubernetes/features/issues/22

- [x] TODO: Call `HandlePluginError` from the webhook backend, once https://github.com/kubernetes/kubernetes/pull/45919 merges (in this or a separate PR, depending on timing of the merge)

/cc @ihmccreery @sttts @soltysh @ericchiang