📖 Update docs for beta ClusterResourceSet

[mboersma]

What this PR does / why we need it:

Updates the documentation (and two manifests) to reflect the status of the ClusterResourceSet experimental feature as Beta and true by default.

When creating a PR to promote the MachinePools experimental feature to Beta / true, it seemed there was similar cleanup that should be done to CRS.

Which issue(s) this PR fixes:
N/A, but see also #10141

/area documentation

[mboersma]

/area clusterresourceset

[killianmuldoon]

Was there a general agreement to promote CRS to beta as well? Do we have an issue covering what's needed here like we do for MachinePools - i.e. #9005?

[mboersma]

AFAICT ClusterResourceSet has been beta already for quite a while:

cluster-api/feature/feature.go

Lines 37 to 41 in af5f2c9

	// ClusterResourceSet is a feature gate for the ClusterResourceSet functionality.
	//
	// alpha: v0.3
	// beta: v0.4
	ClusterResourceSet featuregate.Feature = "ClusterResourceSet"

cluster-api/feature/feature.go

Lines 71 to 75 in af5f2c9

	var defaultClusterAPIFeatureGates = map[featuregate.Feature]featuregate.FeatureSpec{
	// Every feature should be initiated here:
	MachinePool: {Default: false, PreRelease: featuregate.Alpha},
	ClusterResourceSet: {Default: true, PreRelease: featuregate.Beta},
	ClusterTopology: {Default: false, PreRelease: featuregate.Alpha},

So I thought this PR was just catching up with reality by marking it beta in the "experimental features" doc where it was still labeled alpha, and removing all the places where we say "don't forget to turn on this experimental feature." But I may be mistaken.

[killianmuldoon]

I'm really not sure - but this is something that should probably have a tracking issue and be brought up at the community meeting IMO - I'm not sure if a decision was made to turn this on by default in this way but it would be good to make sure.

[mboersma]

/hold

this is something that should probably have a tracking issue and be brought up at the community meeting

I added this as a discussion topic for the March 27th CAPI community meeting.

[mboersma]

/hold cancel

At today's office hours meeting, consensus was that CRS has been beta and that it was an oversight that experimental-features.md didn't reflect this.

[mboersma]

Updated to include great review comments from @neolit123.

[neolit123]

/lgtm
/approve
/hold

pls unhold if no additional review is pending.

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 03f338a8c18b267488151656ab6311ca2cf28164

[sbueringer]

Thank you very much for taking care of this!

/hold cancel
/approve

I would not backport this as I think we shouldn't go from disabled per default to enabled per default in a patch release (for folks using our manager.yaml / components.yaml / clusterctl)

[fabriziopandini]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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