Backport of CSI: Expand Volume (Controller only) into release/1.6.x

[hc-github-team-nomad-core]

Backport

This PR is auto-generated from #18359 to be assessed for backporting due to the inclusion of the label backport/1.6.x.

The below text is copied from the body of the original PR.

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Addresses #10324 with declarative config (instead of a new imperative command/api route).

I still need to update docs, but to trigger a volume increase, modify the volume specification that was used initially to create/register the volume with a higher capacity_min (and optionally capacity_max), then issue create or register again.

This introduces a comparatively very slow process into the create/register flow (if expand is actually needed), and modifies the behavior of create to be more idempotent than it currently is (presently it always issues create to the controller plugin).

I hemmed and hawed a lot on where the validation logic should live, so I'd be happy to hear any suggestions to move any of it. I mainly want to avoid putting it right before writing to raft, because by that point reality (a real live disk in the world) may have already changed.

The commit history is messy right now; I intend to squash it before merging.

So far this covers ControllerExpandVolume to increase volumes outside of the instance (e.g. an AWS EBS volume), but does not yet complete the process (when required) with NodeExpandVolume on the node where the volume is mounted. I think I'll make that a separate PR.

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Overview of commits

• c6dbba7