[HUDI-3457] Refactored Spark DataSource Relations to avoid code duplication (#4877)

Refactoring Spark DataSource Relations to avoid code duplication. 

Following Relations were in scope:

- BaseFileOnlyViewRelation
- MergeOnReadSnapshotRelaation
- MergeOnReadIncrementalRelation

hudi-client/hudi-spark-client/src/main/scala/org/apache/hudi/HoodieConversionUtils.scala

@@ -0,0 +1,29 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.hudi
+
+object HoodieConversionUtils {
+
+  def toJavaOption[T](opt: Option[T]): org.apache.hudi.common.util.Option[T] =
+    if (opt.isDefined) org.apache.hudi.common.util.Option.of(opt.get) else org.apache.hudi.common.util.Option.empty()
+
+  def toScalaOption[T](opt: org.apache.hudi.common.util.Option[T]): Option[T] =
+    if (opt.isPresent) Some(opt.get) else None
+
+}

hudi-client/hudi-spark-client/src/main/scala/org/apache/hudi/HoodieSparkUtils.scala

@@ -118,11 +118,6 @@ object HoodieSparkUtils extends SparkAdapterSupport {
     })
   }
 
-  def createInMemoryFileIndex(sparkSession: SparkSession, globbedPaths: Seq[Path]): InMemoryFileIndex = {
-    val fileStatusCache = FileStatusCache.getOrCreate(sparkSession)
-    new InMemoryFileIndex(sparkSession, globbedPaths, Map(), Option.empty, fileStatusCache)
-  }
-
   /**
    * @deprecated please use other overload [[createRdd]]
    */