🌱 deprecate rolloutAfter in cluster topology

[ykakarap]

What this PR does / why we need it:

Cluster.spec.topology.rolloutAfter is currently unused and does not provide any functionality.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Based on: #5218 (comment)

[ykakarap]

Follow-up: To add an entry for this in the v1.4-to-v1.5 page in the CAPI book once the page is ready.

[sbueringer]

Follow-up: To add an entry for this in the v1.4-to-v1.5 page in the CAPI book once the page is ready.

Is this relevant to provider authors?
(Just noticing that we want to add a lot of stuff to the document which doesn't seem to be relevant to provider authors, probably because of a lack of being able to write user-facing notes)

[sbueringer]

+1 for the deprecation in general

Also +1 to cherry-pick into v1.4. In any case we would remove the field with v1beta2, but it's better if we communicate the deprecation / that the field has no function as early as possible.

[sbueringer]

/lgtm

[k8s-ci-robot]

LGTM label has been added.

Git tree hash: 5c82f749363b5e61f8257ff711950ce60b9eef5a

[killianmuldoon]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

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[killianmuldoon]

/cherry-pick release-1.4

[k8s-infra-cherrypick-robot]

@killianmuldoon: once the present PR merges, I will cherry-pick it on top of release-1.4 in a new PR and assign it to you.

In response to this:

/cherry-pick release-1.4

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[k8s-infra-cherrypick-robot]

@killianmuldoon: new pull request created: #8326

In response to this:

/cherry-pick release-1.4

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[elmiko]

discussed this on the meeting today, several +1s

[johannesfrey]

/area clusterclass