kvserverpb: mark probe requests' replicated cmds as IsTrivial

That way, they won't each request their own `replicaAppBatch`. They were wildly
inefficient to apply before this commit, which played a role in a recent
incident[^1].

[^1]: cockroachlabs/support#2287

Epic: none
Release note: None

pkg/kv/kvserver/kvserverpb/proposer_kv.go

@@ -74,6 +74,7 @@ func (r *ReplicatedEvalResult) IsTrivial() bool {
 	allowlist.Delta = enginepb.MVCCStatsDelta{}
 	allowlist.WriteTimestamp = hlc.Timestamp{}
 	allowlist.PrevLeaseProposal = nil
+	allowlist.IsProbe = false // probes are trivial, they always get refused in CheckForcedErr
 	allowlist.State = nil
 	return allowlist.IsZero()
 }