spanconfig: address fallout after enabling-by-default

[irfansharif]

Describe the problem

We recently enabled span configs by default: #73876. Given the blast radius, we expect it to non-trivial CI impact. This issue tracks (post-hoc) relevant flakes/investigations.

• importccl: TestCSVImportCanBeResumed failed under testrace #74932 (and 100+ race failures) fixed
• kv/kvserver: TestReplicateQueueUpAndDownReplicateNonVoters failed #74995 fixed
• ccl/backupccl: TestPaginatedBackupTenant failed #74928 fixed
• tracing: panic due to "getting first from empty ring buffer" #75045 fixed
• sql: TestTelemetry failed #75190 fixed
• kv/kvserver: TestReplicateQueueUpAndDownReplicateNonVoters failed #75135 fixed
• kv/kvserver: TestBackpressureNotAppliedWhenReducingRangeSize failed #75109 fixed, fixed again
• kv/kvserver: TestStoreSplitRangeLookupRace failed #75198 fixed
• sql/opt/exec/execbuilder: TestExecBuild failed #74933 fixed
• kv/kvserver: TestProtectedTimestamps failed #75020 fixed
• sql: unskip disable-span-config 5node tests #75282 fixed
• ccl/backupccl: TestGCDropIndexSpanExpansion failed #75202 fixed
• roachtest: knex failed #74021 ruled out
• kv/kvserver: TestRangefeedCheckpointsRecoverFromLeaseExpiration failed #75098 fixed
• ccl/multiregionccl: TestMultiRegionDataDriven failed #74783 ignored
• bench/rttanalysis: TestBenchmarkExpectation failed #74396 ignored
• sql/logictest: TestLogic failed #75570 fixed
• kv/kvserver: TestBackpressureNotAppliedWhenReducingRangeSize failed #75609 fixed
• sql: TestDistSQLFlowsVirtualTables failed #75208 fixed
• spanconfig: investigate slowdown of combined-statements API with span configs #74919
• backupccl: TestFullClusterBackup/ensure_that_jobs_are_restored flakes under span configs #75060
• changefeedccl: flakey TestChangefeedRestartDuringBackfill #75080
• cli: TestRemoveDeadReplicas failed #75133

[irfansharif]

There are still a few outstanding tests, but looking at the build success rate from last week (the dip here was the fallout), I think we've addressed most of what we needed to to get back to pre-span config levels. We're not finding much in the way of real bugs in the infra, mostly just tests that need updating, so I'll stop combing for issues through TC/bors/etc. Closing.