kvnemesis: support non-transactional DelRange operations

[AlexTalks]

Currently DelRange operations are only generated inside of transactions in kvnemesis. We should also add support for these operations outside of transactions, if we can determine a way to validate the delete on each key atomically without relying on the timestamp of the transaction to identify the stored delete tombstones that were written by the operation.

Jira issue: CRDB-9701

[tbg]

Relevant snippet

cockroach/pkg/kv/kvnemesis/validator.go

Lines 383 to 416 in 6ee6501

	case *DeleteRangeOperation:
	if txnID == nil {
	v.checkAtomic(`deleteRange`, t.Result, nil, op)
	} else {
	// For the purposes of validation, DelRange operations decompose into
	// a specialized scan for keys with non-nil values, followed by
	// writes for each key, with a span to validate that the keys we are
	// deleting are within the proper bounds. See above comment for how
	// the individual deletion tombstones for each key are validated.
	scan := &observedScan{
	Span: roachpb.Span{
	Key: t.Key,
	EndKey: t.EndKey,
	},
	IsDeleteRange: true,
	KVs: make([]roachpb.KeyValue, len(t.Result.Keys)),
	}
	deleteOps := make([]observedOp, len(t.Result.Keys))
	for i, key := range t.Result.Keys {
	scan.KVs[i] = roachpb.KeyValue{
	Key: key,
	Value: roachpb.Value{},
	}
	write := &observedWrite{
	Key: key,
	Value: roachpb.Value{},
	IsDeleteRange: true,
	}
	deleteOps[i] = write
	}
	v.observedOpsByTxn[*txnID] = append(v.observedOpsByTxn[*txnID], scan)
	v.observedOpsByTxn[*txnID] = append(v.observedOpsByTxn[*txnID], deleteOps...)
	}
	case *ScanOperation:

[blathers-crl]

cc @cockroachdb/replication