c/p_leaders: check if leaders table was modified after async iteration

[mmaslankaprv]

Since leaders table might have been modified during the execution of iteration over the topic partitions we must check the version of topics table after the asynchronous iteration finished.

Backports Required

• none - not a bug fix
• none - this is a backport
• none - issue does not exist in previous branches
• none - papercut/not impactful enough to backport
• v23.3.x
• v23.2.x
• v23.1.x

Release Notes

• none

[StephanDollberg]

Don't we need the same in update_with_node_report?

[mmaslankaprv]

Don't we need the same in update_with_node_report?

no, as in node report we iterate over the report itself so the change of partition leaders table version doesn't matter, what matters is to check before accessing previously found t_it which is done inside the async loop. In other words iterator of outer loop will not be invalidated as the node_report.topics doesn't change

[vbotbuildovich]

/backport v23.3.x

[vbotbuildovich]

Failed to create a backport PR to v23.3.x branch. I tried:

git remote add upstream https://github.com/redpanda-data/redpanda.git
git fetch --all
git checkout -b backport-pr-16711-v23.3.x-498 remotes/upstream/v23.3.x
git cherry-pick -x 625fb441ffccadfe476a2a924247dfef8aeb1066 6eaa7b8278bbcc1ccbb3173e4d1ed98e2ac73175

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