[SPARK-49426][CONNECT][SQL] Create a shared interface for DataFrameWr…

…iterV2

### What changes were proposed in this pull request?
This PR creates a shared interface for DataFrameWriterV2.

### Why are the changes needed?
We are creating a shared Scala Spark SQL interface for Classic and Connect.

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

### How was this patch tested?
Existing tests.

### Was this patch authored or co-authored using generative AI tooling?
No.

Closes apache#47962 from hvanhovell/SPARK-49426.

Authored-by: Herman van Hovell <herman@databricks.com>
Signed-off-by: Herman van Hovell <herman@databricks.com>

connector/connect/client/jvm/src/main/scala/org/apache/spark/sql/Dataset.scala

@@ -37,7 +37,7 @@ import org.apache.spark.sql.connect.common.{DataTypeProtoConverter, StorageLevel
 import org.apache.spark.sql.errors.DataTypeErrors.toSQLId
 import org.apache.spark.sql.expressions.SparkUserDefinedFunction
 import org.apache.spark.sql.functions.{struct, to_json}
-import org.apache.spark.sql.internal.{ColumnNodeToProtoConverter, DataFrameWriterImpl, ToScalaUDF, UDFAdaptors, UnresolvedAttribute, UnresolvedRegex}
+import org.apache.spark.sql.internal.{ColumnNodeToProtoConverter, DataFrameWriterImpl, DataFrameWriterV2Impl, ToScalaUDF, UDFAdaptors, UnresolvedAttribute, UnresolvedRegex}
 import org.apache.spark.sql.streaming.DataStreamWriter
 import org.apache.spark.sql.types.{Metadata, StructType}
 import org.apache.spark.storage.StorageLevel
@@ -1018,27 +1018,9 @@ class Dataset[T] private[sql] (
     new DataFrameWriterImpl[T](this)
   }
 
-  /**
-   * Create a write configuration builder for v2 sources.
-   *
-   * This builder is used to configure and execute write operations. For example, to append to an
-   * existing table, run:
-   *
-   * {{{
-   *   df.writeTo("catalog.db.table").append()
-   * }}}
-   *
-   * This can also be used to create or replace existing tables:
-   *
-   * {{{
-   *   df.writeTo("catalog.db.table").partitionedBy($"col").createOrReplace()
-   * }}}
-   *
-   * @group basic
-   * @since 3.4.0
-   */
+  /** @inheritdoc */
   def writeTo(table: String): DataFrameWriterV2[T] = {
-    new DataFrameWriterV2[T](table, this)
+    new DataFrameWriterV2Impl[T](table, this)
   }
 
   /**