backupccl: TestBackupRestoreDuringUserDefinedTypeChange panics within tenant

[msbutler]

To reproduce, stress the test on top of https://github.com/cockroachdb/cockroach/pull/88271, with DisableTenantTestTenant set to false.

See test failure artifacts here.

Fresh build reveals more subtests hit the same panic: https://teamcity.cockroachdb.com/viewLog.html?buildId=6576285&buildTypeId=Cockroach_BazelEssentialCi

Jira issue: CRDB-19794

[blathers-crl[bot]]

cc @cockroachdb/disaster-recovery

[stevendanna]

It looks to me like the panic here is actually a timeout. My suspicion here is that our testing hooks aren't property flowing through to the testing server so we are waiting forever on one of these channel selects.

[ajwerner]

I'm taking this off the schema board.