*: add test for enable new replica selector by default (#51793)

close #51792

pkg/config/config_test.go

@@ -754,6 +754,7 @@ store-limit=0
 ttl-refreshed-txn-size=8192
 resolve-lock-lite-threshold = 16
 copr-req-timeout = "120s"
+enable-replica-selector-v2 = false
 [tikv-client.async-commit]
 keys-limit=123
 total-key-size-limit=1024
@@ -804,6 +805,8 @@ max_connections = 200
 	require.Equal(t, uint(6000), conf.TiKVClient.RegionCacheTTL)
 	require.Equal(t, int64(0), conf.TiKVClient.StoreLimit)
 	require.Equal(t, int64(8192), conf.TiKVClient.TTLRefreshedTxnSize)
+	require.Equal(t, false, conf.TiKVClient.EnableReplicaSelectorV2)
+	require.Equal(t, true, defaultConf.TiKVClient.EnableReplicaSelectorV2)
 	require.Equal(t, uint(1000), conf.TokenLimit)
 	require.True(t, conf.EnableTableLock)
 	require.Equal(t, uint64(5), conf.DelayCleanTableLock)