sctest: unskip multitenant for schema change tests

This fixes external process tenant startup to propagate
version settings from the parent, allowing tenants to start
when the cluster is running at an older version
(e.g., MinSupported).

Note that MultiRegionTestClusterFactory already allowed
multitenant testing.

Release note: None

Author: rafiss

pkg/server/testserver.go

@@ -637,6 +637,14 @@ func (ts *testServer) startDefaultTestTenant(
 ) (serverutils.ApplicationLayerInterface, error) {
 	tenantSettings := cluster.MakeTestingClusterSettings()
 	if st := ts.params.Settings; st != nil {
+		// Use the same version constraints as the parent settings so that
+		// external process tenants can start when the cluster is running at
+		// a version older than Latest.
+		tenantSettings = cluster.MakeTestingClusterSettingsWithVersions(
+			st.Version.LatestVersion(),
+			st.Version.MinSupportedVersion(),
+			false, /* initializeVersion */
+		)
 		// Copy overrides and other test-specific configuration,
 		// as a convenience for test writers that do the following:
 		// - create a new Settings

pkg/sql/schemachanger/sctest/backup.go

@@ -355,6 +355,11 @@ func backupSuccess(t *testing.T, args backupSuccessTestArgs, cs CumulativeTestCa
 	}
 
 	// Upgrade the cluster if applicable.
+	if args.server.Server.StartedDefaultTestTenant() {
+		sysDB := args.server.Server.SystemLayer().SQLConn(t)
+		_, err := sysDB.Exec("SET CLUSTER SETTING VERSION = $1", clusterversion.Latest.String())
+		require.NoError(t, err)
+	}
 	tdb.Exec(t, "SET CLUSTER SETTING VERSION = $1", clusterversion.Latest.String())
 
 	// Restore the backup of the database taken mid-successful-schema-change

pkg/sql/schemachanger/sctest/test_server_factory.go

@@ -117,7 +117,6 @@ func (f SingleNodeTestClusterFactory) Start(ctx context.Context, t *testing.T) T
 				UseTransactionalDescIDGenerator: true,
 			},
 		},
-		DefaultTestTenant: base.TestDoesNotWorkWithSecondaryTenantsButWeDontKnowWhyYet(142814),
 	}
 	if f.server != nil {
 		args.Knobs.Server = f.server