Add skip-health-check annotation for managed resources

[shafeeqes]

How to categorize this PR?

/area usability
/kind enhancement

What this PR does / why we need it:
This PR introduces an annotation resources.gardener.cloud/skip-health-check. If this annotation is set to true, then resource-manager will skip health check for this resource, and ResourcesHealthy for the MR would be True even if this resource is unhealthy. Also the ResourcesProgressing condition will be set to False even if the resource hasn't been fully rolled out yet (In case of statefulsets, deployments and daemonsets).

This annotation has been set to true for reserve-excess-capacity deployment by default, so that the seed can get Ready even if this pod is stuck in pending.

Which issue(s) this PR fixes:
Fixes #6275

Special notes for your reviewer:

Release note:

If a resource in the `ManagedResource` is annotated with `resources.gardener.cloud/skip-health-check=true` then the resource will be skipped during health checks by the health controller. The ManagedResource conditions will not reflect the health condition of this resource anymore. The `ResourcesProgressing` condition will also be set to `False`.

[gardener-prow]

@shafeeqes: 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-gardener-apidiff	fe9719d	link	false	/test pull-gardener-apidiff

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[ary1992]

/assign

[ary1992]

Thanks for the PR :)
/lgtm

[rfranzke]

Nice PR, well structured!
/lgtm

[rfranzke]

/approve

[gardener-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: rfranzke

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