[Feature][Gerrit] Add Dependency Priorities & Create Relation-chains on Gerrit

[Chrimle]

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Basically, whenever Renovate create dependency bumps, rebase changes on-top of each other, in the order by user-specified priority. By default, all dependency bumps will have equal priority, and thus will create separated changes.

The reason why this would be "neat", is that if fast-forward-only is enabled, each Renovate change needs to be rebased once another Renovate change has been merged to main/master.

So, since it may (or may not) be a manual review process, there's sometime a need to approve and submit dependencies in certain orders. Perhaps by internal/external dependencies. Or low-risk/high-risk. Whatever it is, the once one change is merged, the other pending changes needs to be rebased. Relation-chains solves this issue.

Related #39761