kvserver: skip some slow tests under race

These take >1m under race and are now skipped for the race build.

Note that TestLearnerSnapshotFailsRollback takes 90s even under ideal
conditions, though that is fixed once I get #75248 over the finish
line. At that point it probably wouldn't figure prominently as a
slow test, but until then it's verrrry slow (>7m, probably since
race stuff slows down the longer it runs) so still good to skip
it now.

https://cockroachlabs.slack.com/archives/C0KB9Q03D/p1646221664032729

Release justification: testing-only change
Release note: None

pkg/kv/kvserver/client_merge_test.go

@@ -417,6 +417,7 @@ func TestStoreRangeMergeTimestampCache(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)
 	skip.UnderShort(t)
+	skip.UnderRace(t)
 
 	testutils.RunTrueAndFalse(t, "disjoint-leaseholders", func(t *testing.T, disjointLeaseholders bool) {
 		testutils.RunTrueAndFalse(t, "through-snapshot", func(t *testing.T, throughSnapshot bool) {
@@ -4465,6 +4466,8 @@ func TestMergeQueueSeesNonVoters(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)
 
+	skip.UnderRace(t)
+
 	type test struct {
 		name                                                   string
 		leftVoters, rightVoters, leftNonVoters, rightNonVoters []int

pkg/kv/kvserver/closed_timestamp_test.go

@@ -606,6 +606,8 @@ func TestClosedTimestampFrozenAfterSubsumption(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)
 
+	skip.UnderRace(t)
+
 	for _, test := range []struct {
 		name string
 		// transferLease, if set, will be called while the RHS is subsumed in order

pkg/kv/kvserver/replica_closedts_test.go

@@ -28,6 +28,7 @@ import (
 	"github.com/cockroachdb/cockroach/pkg/server"
 	"github.com/cockroachdb/cockroach/pkg/testutils"
 	"github.com/cockroachdb/cockroach/pkg/testutils/serverutils"
+	"github.com/cockroachdb/cockroach/pkg/testutils/skip"
 	"github.com/cockroachdb/cockroach/pkg/testutils/sqlutils"
 	"github.com/cockroachdb/cockroach/pkg/testutils/testcluster"
 	"github.com/cockroachdb/cockroach/pkg/util/hlc"
@@ -45,6 +46,9 @@ import (
 func TestBumpSideTransportClosed(t *testing.T) {
 	defer leaktest.AfterTest(t)()
 	defer log.Scope(t).Close(t)
+
+	skip.UnderRace(t)
+
 	ctx := context.Background()
 
 	type setupArgs struct {

pkg/kv/kvserver/replica_learner_test.go

@@ -312,6 +312,7 @@ func TestLearnerSnapshotFailsRollback(t *testing.T) {
 	defer log.Scope(t).Close(t)
 
 	skip.UnderShort(t) // Takes 90s.
+	skip.UnderRace(t)
 
 	runTest := func(t *testing.T, replicaType roachpb.ReplicaType) {
 		var rejectSnapshots int64