chore: Merge metrics to fire singleton metrics to controller_runtime metric namespace

[jonathan-innis]

Fixes #

Description

• Migrate all singleton metrics inside of the controller_runtime namespace by leveraging prometheus AlreadyRegisteredError to grab the already registered collector and fire metrics to the same namespace

How was this change tested?

make presubmit

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[coveralls]

Pull Request Test Coverage Report for Build 4306702662

• 21 of 48 (43.75%) changed or added relevant lines in 8 files are covered.
• 3 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+0.2%) to 80.999%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/controllers/metrics/state/controller.go	0	1	0.0%
pkg/controllers/provisioning/controller.go	0	1	0.0%
pkg/operator/controller/singleton.go	16	41	39.02%

Files with Coverage Reduction	New Missed Lines	%
pkg/operator/controller/singleton.go	3	20.0%

Totals
Change from base Build 4266917395:	0.2%
Covered Lines:	6390
Relevant Lines:	7889

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💛 - Coveralls

[bwagner5]

I'd rather start the conversation of upstreaming these controllers rather than doing this hack that we'll have to maintain. It doesn't seem like the maintenance would be that much (I don't see controller-runtime removing these metrics), but maybe some get added that we have to stay in-sync with. Without a clear ask where this is actually helping someone, I'd rather not do this.

[jonathan-innis]

I'd rather start the conversation of upstreaming these controllers rather than doing this hack that we'll have to maintain. It doesn't seem like the maintenance would be that much (I don't see controller-runtime removing these metrics), but maybe some get added that we have to stay in-sync with. Without a clear ask where this is actually helping someone, I'd rather not do this.

I think that conversation should happen either way; however, we've already taken on the burden of maintaining the same controller metrics as controller_runtime (in part because they are really useful for customers to see what's going on across the controllers). So I think that either way, all of these metrics should make it in for us, either under the controller_runtime namespace or under the karpenter_controller namespace.

I think what's more controversial is if they should be under the same namespace using this "hack." While I don't love it, I think that prometheus recognizes this as a supported method of switching over between a metric that is already registered so I don't really worry about them removing that.

[bwagner5]

LGTM

[jonathan-innis]

Linking the relevant controller-runtime issue that tracks the SingletonController: kubernetes-sigs/controller-runtime#2220