Currently, an ExportRequest will take an extremely long time to resolve a collection of abandoned intents. This can make it look like the ExportRequest is stuck somewhere in KV. The reason for this (or at least part of it) is that ExportMVCCToSst currently only returns a single intent if it returns a WriteIntentError. This is different than a request like ScanRequest, which will collect a set of intents in a WriteIntentError, which allows higher levels to process all of them at once.

We should improve ExportRequest to collect multiple intents in a single WriteIntentError.

We should also write a test that exercises the path where an ExportRequest needs to clean up millions of abandoned intents.

gz#7529

Epic: CRDB-2554