📖 documentation for clusterctl alpha topology plan

[ykakarap]

What this PR does / why we need it:

Adds documentation for the new clusterctl alpha topology plan command.

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 #

[sbueringer]

xref: #5953

[sbueringer]

Looks good to me!

One potential additional use case could be modifying something in the Cluster topology while the ClusterClass stays the same

[fabriziopandini]

That a great start!
Main comments

• let's drop dry run and use plan
• let's move Reference at the end (as well as the notes about corners cases/details)
• let's add two use cases
  • change topology
  • rebase

[fabriziopandini]

This looks great!
last round of nits from my side (and you can remove WIP as well)

[fabriziopandini]

/lgtm
@sbueringer PTAL

[sbueringer]

Thx, great work! I think it explains very nicely what you can achieve with the topology plan command

/lgtm

[fabriziopandini]

/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fabriziopandini

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[fabriziopandini]

/cherry-pick release-1.1

[k8s-infra-cherrypick-robot]

@fabriziopandini: new pull request created: #6023

In response to this:

/cherry-pick release-1.1

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