Added a support of com.memsql.spark data source name

Summary:
Added a support of com.memsql.spark data source name

**Design doc/spec**:
**Docs impact**: none

Test Plan: Ran the changed test locally

Reviewers: carl, iblinov-ua, roxanna

Reviewed By: carl

Subscribers: engineering-list

Differential Revision: https://grizzly.internal.memcompute.com/D45603

src/main/resources/META-INF/services/org.apache.spark.sql.sources.DataSourceRegister

@@ -1,2 +1,2 @@
 com.singlestore.spark.DefaultSource
-com.singlestore.spark.MemsqlDefaultSource
+com.memsql.spark.DefaultSource

src/main/scala/com/memsql/spark/DefaultSource.scala

@@ -0,0 +1,8 @@
+package com.memsql.spark
+
+import com.singlestore.spark
+
+class DefaultSource extends spark.DefaultSource {
+
+  override def shortName(): String = spark.DefaultSource.MEMSQL_SOURCE_NAME_SHORT
+}

src/test/scala/com/singlestore/spark/LoadDataTest.scala

@@ -210,15 +210,23 @@ class LoadDataTest extends IntegrationSuiteBase with BeforeAndAfterEach with Bef
     assertLargeDataFrameEquality(actualDF, df)
   }
 
-  it("should work with `memsql` source") {
+  it("should work with `memsql` and `com.memsql.spark` source") {
     df = spark.createDF(
       List((5, "E", 50)),
       List(("id", IntegerType, true), ("name", StringType, true), ("age", IntegerType, true))
     )
     writeTable("testdb.loaddata", df, SaveMode.Append)
 
-    val actualDF =
+    val actualDFShort =
       spark.read.format(DefaultSource.MEMSQL_SOURCE_NAME_SHORT).load("testdb.loaddata")
+    assertSmallDataFrameEquality(
+      actualDFShort,
+      spark.createDF(
+        List((5, "E", 50)),
+        List(("id", IntegerType, true), ("name", StringType, true), ("age", IntegerType, true))
+      ))
+    val actualDF =
+      spark.read.format(DefaultSource.MEMSQL_SOURCE_NAME).load("testdb.loaddata")
     assertSmallDataFrameEquality(
       actualDF,
       spark.createDF(