[Cherry-Pick] Use calico_pool_blocksize from cluster when existing (#10516)

[cyclinder]

The blockSize attribute from Calico IPPool resources cannot be changed once set 1. Consequently, we use the one currently defined when configuring the existing IPPool, avoiding upgrade errors by trying to change it.

In particular, this can be useful when calico_pool_blocksize default changes in kubespray, which would otherwise force users to add an explicit setting to their inventories.

What type of PR is this?

Uncomment only one /kind <> line, hit enter to put that in a new line, and remove leading whitespaces from that line:

/kind api-change

/kind bug

/kind cleanup
/kind design
/kind documentation
/kind failing-test
/kind feature
/kind flake

What this PR does / why we need it:

The blockSize attribute from Calico IPPool resources cannot be changed
once set 1. Consequently, we use the one currently defined when
configuring the existing IPPool, avoiding upgrade errors by trying to
change it.

Which issue(s) this PR fixes:

#9055 (comment)

Special notes for your reviewer:

this PR cherry-pick #10516 to release-2.20

Does this PR introduce a user-facing change?:

[k8s-ci-robot]

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[VannTen]

Be aware that this does not completely advert the need to explicitly set calico_pool_blocksize in inventories (unfortunately). There is a check (in preinstall, I think) which verify that we have the correct blocksize, I need to change that as well. Didn't had time for that yet unfortunately

[cyclinder]

Be aware that this does not completely advert the need to explicitly set calico_pool_blocksize in inventories (unfortunately).

At least, We can make sure it will work by default(If we don't set calico_pool_blocksize). Right?

[VannTen]

Be aware that this does not completely advert the need to explicitly set calico_pool_blocksize in inventories (unfortunately).

At least, We can make sure it will work by default(If we don't set calico_pool_blocksize). Right?

No, precisely. There is another check in preinstall which check that calico_pool_blocksize == the one from the cluster, and since calico_pool_blocksize has a default... We should remove that check I think but I haven't taken the time to do the PR yet.

[floryut]

2.20 is no longer supported, moving to close this one, don't hesitate to comment/reach on slack if it seems extreme 👍