remove apiserver_admission_step_admission_duration_seconds_summary me…

[chadpatel]

Description:
The apiserver_admission_step_admission_duration_seconds_summary was getting included in our regex. We only intended to publish The apiserver_admission_step_admission_duration_seconds, which is made up of prometheus (submetrics? idk what to call them), The apiserver_admission_step_admission_duration_seconds_[count/sum/bucket], because this is a prometheus histogram. We need to allow list the component bits but exclude the summary metric itself

I also decided to prefix our regex with a carrot as a performance optimization. it is unnecessary for the entire metric name to be scanned to determine if it matches, with the carrot it will be able to determine just from the first couple characters if it is a match or not.

An alternative implementation would be to replace all the ".*"s, which are super convenient, with very explicit matchers for the histogram. Something like this:

	controlPlaneMetricAllowList = []string{
		"apiserver_admission_controller_admission_duration_seconds_(bucket|sum|count)$",
		// we want to exclude the separate metric apiserver_admission_step_admission_duration_seconds_summary
		"^apiserver_admission_step_admission_duration_seconds_(bucket|sum|count)$",
		"^apiserver_admission_webhook_admission_duration_seconds_(bucket|sum|count)$",
		"^apiserver_current_inflight_requests",
		"^apiserver_current_inqueue_requests",
		"^apiserver_flowcontrol_rejected_requests_total",
		"^apiserver_flowcontrol_request_concurrency_limit",
		"^apiserver_longrunning_requests",
		"^apiserver_request_duration_seconds_(bucket|sum|count)$",
		"^apiserver_request_total",
		"^apiserver_requested_deprecated_apis",
		"^apiserver_storage_list_duration_seconds_(bucket|sum|count)$",
		"^apiserver_storage_objects",
		"^apiserver_storage_db_total_size_in_bytes_(bucket|sum|count)$",
		"^apiserver_storage_size_bytes_(bucket|sum|count)$",
		"^etcd_db_total_size_in_bytes_(bucket|sum|count)$",
		"^etcd_request_duration_seconds_(bucket|sum|count)$",
		"^rest_client_request_duration_seconds_(bucket|sum|count)$",
		"^rest_client_requests_total",
	}

LMK what you think about that

Link to tracking Issue:

Testing: Tested on my cluster
control plane metrics are still flowing:

no summary metric:

but the non-summary one is still flowing

Documentation: N/A, the removed metric was unintended so it was never documented as a supported metric

[SaxyPandaBear]

LGTM