kubeadm: organize phases cmd

[fabriziopandini]

What type of PR is this?
/kind cleanup

What this PR does / why we need it:
Reorganize cmd for phases, by separating init phases and join phases

Which issue(s) this PR fixes:
none

Special notes for your reviewer:
While splitting the control-plane-prepare phase, I simplified the manifest subphase in order to avoid the third level of nested phases (if we want to add this, we should do this consistently for certs, kubeconfig and manifests)

Does this PR introduce a user-facing change?:

NONE

/sig cluster-lifecycle
/area kubeadm
/priority backlog
@kubernetes/sig-cluster-lifecycle-pr-reviews
/assign @neolit123
/assign @ereslibre
@MalloZup

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: fabriziopandini

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[yagonobre]

Thanks @fabriziopandini
/lgtm

[ereslibre]

/lgtm

[fabriziopandini]

Removing WIP as per comments/feedbacks on slack

[chuckha]

@fabriziopandini was there an issue for this or could you link to slack where this discussion took place? I'm interested in knowing the reason behind this work. It looks very relevant to this comment I made yesterday: kubernetes/kubeadm#1375 (comment)

[fabriziopandini]

@chuckha here it is the thread for better visibility, I'm going to add a comment to 1375

@fabriziopandini

Hi all, just sent #73725
It re-organize phases, by splitting init phases and join phases + I simplified
the manifest subphase in order to avoid the third level of nested phases (if we want to
add this, we should do this consistently for certs, kubeconfig and manifests)
it is still a WIP because those are changes not agreed before
let me know if you are fine with those changes or not

@neolit123

i think this is great 👍

@ereslibre

1. I think subdirectories as you did is a better approach than sibling files as I first started,
2. I think it makes sense to remove the subphases for manifests because we are not coherent
   with subphases in certs and kubeconfig so yes, 👍 from me, the organization is clearly better