use generic slis as entrypoint for healthcheck metrics

[logicalhan]

...and expose convenience functions for setting stuff up

What type of PR is this?

/kind cleanup

What this PR does / why we need it:

We need some convenience functions for wiring up component health SLI metrics. This accomplishes that.

Special notes for your reviewer:

Does this PR introduce a user-facing change?

NONE

[k8s-ci-robot]

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[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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[dashpole]

/lgtm
/hold
for other reviewers to have a chance to comment

[logicalhan]

/hold cancel

(got another PR blocked behind this one)

[k8s-ci-robot]

@logicalhan: The following test failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-kubernetes-e2e-kind	63f98e0	link	unknown	/test pull-kubernetes-e2e-kind

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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[logicalhan]

/retest