CSI: claim releases don't need to go thru GC eval

[tgross]

Following the new volumewatcher in #7794 and performance improvements to it that landed afterwards, there's no particular reason we should be threading claim releases through the GC eval rather than writing an empty CSIVolumeClaimRequest with the mode set to CSIVolumeClaimRelease, just as the GC evaluation would do.

This will reduce the amount of raft writes by 1 and reduce cross-server RPCs by 1 for each volume we release claims on.

These are the two places to replace new evals with de-duplicated CSIVolumeClaimBatchRequests:

• job_endpoint.go#Job.Deregister
• node_endpoint.go#Node.UpdateAlloc

[github-actions]

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