[SPARK-50614][SQL] Revert API change for shredding

### What changes were proposed in this pull request?

#49234 changed the `setSchema` method of ParquetWriteSupport to add a shredding schema parameter. To avoid the risk of breaking libraries that call `setSchema`, this PR instead creates a separate `setShreddingSchema` method to set the shredding schema. If not called, shredding will not be used.

### Why are the changes needed?

Avoid breaking API.

### Does this PR introduce _any_ user-facing change?

No, the feature has not been released yet.

### How was this patch tested?

Existing unit tests.

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes #49353 from cashmand/fix_set_schema.

Authored-by: cashmand <david.cashman@databricks.com>
Signed-off-by: Wenchen Fan <wenchen@databricks.com>

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetUtils.scala

@@ -485,7 +485,8 @@ object ParquetUtils extends Logging {
     }
 
     // This metadata is useful for keeping UDTs like Vector/Matrix.
-    ParquetWriteSupport.setSchema(dataSchema, conf, shreddingSchema)
+    ParquetWriteSupport.setSchema(dataSchema, conf)
+    shreddingSchema.foreach(ParquetWriteSupport.setShreddingSchema(_, conf))
 
     // Sets flags for `ParquetWriteSupport`, which converts Catalyst schema to Parquet
     // schema and writes actual rows to Parquet files.

sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/parquet/ParquetWriteSupport.scala

@@ -539,14 +539,14 @@ object ParquetWriteSupport {
   val SPARK_VARIANT_SHREDDING_SCHEMA: String =
     "org.apache.spark.sql.parquet.variant.shredding.attributes"
 
-  def setSchema(schema: StructType, configuration: Configuration,
-      shreddingSchema: Option[StructType]): Unit = {
+  def setSchema(schema: StructType, configuration: Configuration): Unit = {
     configuration.set(SPARK_ROW_SCHEMA, schema.json)
     configuration.setIfUnset(
       ParquetOutputFormat.WRITER_VERSION,
       ParquetProperties.WriterVersion.PARQUET_1_0.toString)
-    shreddingSchema.foreach { s =>
-      configuration.set(SPARK_VARIANT_SHREDDING_SCHEMA, s.json)
-    }
+  }
+
+  def setShreddingSchema(shreddingSchema: StructType, configuration: Configuration): Unit = {
+    configuration.set(SPARK_VARIANT_SHREDDING_SCHEMA, shreddingSchema.json)
   }
 }