[MINOR][CONNECT][TESTS] Check named parameters in sql()

### What changes were proposed in this pull request?
In the PR, I propose to add new tests to check named parameters in `sql()` of Scala connect client.

### Why are the changes needed?
To improve test coverage. Before the PR, the feature has not been tested at all.

### Does this PR introduce _any_ user-facing change?
No.

### How was this patch tested?
By running new test:
```
$ build/sbt -Phive-2.3 -Phive-thriftserver "test:testOnly *.ClientE2ETestSuite"
```

Closes apache#41726 from MaxGekk/test-named-params-proto.

Authored-by: Max Gekk <[email protected]>
Signed-off-by: Max Gekk <[email protected]>

Author: MaxGekk

connector/connect/client/jvm/src/test/scala/org/apache/spark/sql/ClientE2ETestSuite.scala

@@ -960,6 +960,17 @@ class ClientE2ETestSuite extends RemoteSparkSession with SQLHelper with PrivateM
     assert(result2(0).getInt(0) === 1)
     assert(result2(0).getString(1) === "abc")
   }
+
+  test("sql() with named parameters") {
+    val result0 = spark.sql("select 1", Map.empty[String, Any]).collect()
+    assert(result0.length == 1 && result0(0).getInt(0) === 1)
+
+    val result1 = spark.sql("select :abc", Map("abc" -> 1)).collect()
+    assert(result1.length == 1 && result1(0).getInt(0) === 1)
+
+    val result2 = spark.sql("select :c0 limit :l0", Map("l0" -> 1, "c0" -> "abc")).collect()
+    assert(result2.length == 1 && result2(0).getString(0) === "abc")
+  }
 }
 
 private[sql] case class MyType(id: Long, a: Double, b: Double)