[KYUUBI #2287] Revamp Flink IT by random port and merge tests

### _Why are the changes needed?_

Flink IT shall use random-available port for kyuubi server
we shall merge ITs to prevent creating duplicated servers and engines

### _How was this patch tested?_
- [ ] Add some test cases that check the changes thoroughly including negative and positive cases if possible

- [ ] Add screenshots for manual tests if appropriate

- [ ] [Run test](https://kyuubi.apache.org/docs/latest/develop_tools/testing.html#running-tests) locally before make a pull request

Closes #2287 from yaooqinn/flink.

Closes #2287

a0acce2 [Kent Yao] Revamp Flink IT by random port and merge tests
ad5ae0f [Kent Yao] Revamp Flink IT by random port and merge tests

Authored-by: Kent Yao <yao@apache.org>
Signed-off-by: Kent Yao <yao@apache.org>

integration-tests/kyuubi-flink-it/src/test/scala/org/apache/kyuubi/it/flink/operation/FlinkOperationSuite.scala

@@ -18,15 +18,15 @@
 package org.apache.kyuubi.it.flink.operation
 
 import org.apache.kyuubi.config.KyuubiConf
-import org.apache.kyuubi.config.KyuubiConf.{ENGINE_TYPE, FRONTEND_THRIFT_BINARY_BIND_PORT}
+import org.apache.kyuubi.config.KyuubiConf.ENGINE_TYPE
 import org.apache.kyuubi.it.flink.WithKyuubiServerAndFlinkMiniCluster
 import org.apache.kyuubi.operation.HiveJDBCTestHelper
 import org.apache.kyuubi.operation.meta.ResultSetSchemaConstant.TABLE_CAT
 
 class FlinkOperationSuite extends WithKyuubiServerAndFlinkMiniCluster with HiveJDBCTestHelper {
   override val conf: KyuubiConf = KyuubiConf()
     .set(ENGINE_TYPE, "FLINK_SQL")
-    .set(FRONTEND_THRIFT_BINARY_BIND_PORT, 10019)
+    .set("flink.parallelism.default", "6")
 
   override protected def jdbcUrl: String = getJdbcUrl
 
@@ -50,4 +50,20 @@ class FlinkOperationSuite extends WithKyuubiServerAndFlinkMiniCluster with HiveJ
       assert(resultSet.getString(1) === "tmp.hello")
     }
   }
+
+  test("set kyuubi conf into flink conf") {
+    withJdbcStatement() { statement =>
+      val resultSet = statement.executeQuery("SET")
+      // Flink does not support set key without value currently,
+      // thus read all rows to find the desired one
+      var success = false
+      while (resultSet.next() && !success) {
+        if (resultSet.getString(1) == "parallelism.default" &&
+          resultSet.getString(2) == "6") {
+          success = true
+        }
+      }
+      assert(success)
+    }
+  }
 }