kvserver: load hotspot ignored by allocator starves elastic work

**Note:** This build has runtime assertions enabled. If the same failure was hit in a run without assertions enabled, there should be a similar failure without this message. If there isn't one, then this failure is likely due to an assertion violation or (assertion) timeout.

roachtest.backup-restore/small-ranges [failed](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_Roachtests_RoachtestNightlyGcePrivateBazel/21473094?buildTab=log) with [artifacts](https://teamcity.cockroachdb.com/buildConfiguration/Cockroach_Nightlies_Roachtests_RoachtestNightlyGcePrivateBazel/21473094?buildTab=artifacts#/backup-restore/small-ranges) on release-26.3 @ [9f1d248e7525462838df0bd68f4fd71cce2de6be](https://github.com/cockroachdb/cockroach/commits/9f1d248e7525462838df0bd68f4fd71cce2de6be):

Failed with:

```
(monitor.go:267).Wait: monitor failure: retries exhausted waiting for job 1202761658170081283 to finish
test artifacts and logs in: /artifacts/backup-restore/small-ranges/run_1
```
Cluster Node to Ip Mapping:
| Node | Public IP | Private IP |
| --- | --- | --- |
| teamcity-21473094-1787121479-16-n4cpu4-0001 | | 10.91.97.216 |
| teamcity-21473094-1787121479-16-n4cpu4-0002 | | 10.91.97.217 |
| teamcity-21473094-1787121479-16-n4cpu4-0003 | | 10.91.97.215 |
| teamcity-21473094-1787121479-16-n4cpu4-0004 | | 10.91.96.6 |

Parameters:
- arch=amd64
- cloud=gce
- coverageBuild=false
- cpu=4
- diskCount=0
- encrypted=true
- metamorphicWriteBuffering=true
- runtimeAssertionsBuild=true
Help

See: [roachtest README](https://github.com/cockroachdb/cockroach/blob/master/pkg/cmd/roachtest/README.md)

See: [How To Investigate \(internal\)](https://cockroachlabs.atlassian.net/l/c/SSSBr8c7)

See: [Grafana](https://go.crdb.dev/roachtest-grafana/teamcity-21473094/backup-restore-small-ranges/1787123571286/1787129741723)

See: [Datadog Logs](https://us5.datadoghq.com/logs?query=service%3Aroachtest+%40cluster%3Ateamcity-21473094-1787121479-16-n4cpu4&from_ts=1787123571286&to_ts=1787129741723&live=false&storage=flex_tier)

Same failure on other branches

- #172558 roachtest: backup-restore/small-ranges failed [A-disaster-recovery C-test-failure O-roachtest O-robot P-2 T-disaster-recovery branch-master]

/cc @cockroachlabs/disaster-recovery

[This test on roachdash](https://roachdash.crdb.dev/?filter=status:open%20t:.*backup-restore/small-ranges.*&sort=title+created&display=lastcommented+project) | [Improve this report!](https://github.com/cockroachdb/cockroach/tree/master/pkg/cmd/bazci/githubpost/issues)

Jira issue: CRDB-66874

Start with the roachtest backup-restore/small-ranges failure at monitor.go:267, then inspect the linked artifacts, logs, Grafana dashboard, and related issue #172558. Trace the job timeout and the kvserver allocator's handling of load hotspots; done means identifying and correcting the starvation failure and getting this roachtest to complete successfully.

Written by the indexing model from the issue text.