What changes were proposed in this pull request?

This PR avoids c2r and r2c transition by returning Convention which ouputs both VanillaRow and BatchType for ColumnarWriteFilesExec.

  /**
   * ColumnarWriteFilesExec neither output Row nor columnar data. We output both row and columnar to
   * avoid c2r and r2c transitions. Please note, [[GlutenPlan]] already implement batchType()
   */
  sealed trait ExecuteWriteCompatible extends KnownChildrenConventions with KnownRowType {
   // ...
    override def requiredChildrenConventions(): Seq[ConventionReq] = {
      List(ConventionReq.backendBatch)
    }

    override def rowType(): RowType = {
      RowType.VanillaRow
    }
  }

Why need

ColumnarWriteFilesExec neither outputs Columnar batch data nor InternalRow, and hence we can't add c2r or r2c on top of it, otherwise it would be am internal error.

1. In the normal code path, DataWritingCommandExec is on top of ColumnarWriteFilesExec and DataWritingCommandExec's Convention is VanillaRow which avoid c2r transition.
2. In ClickHouse Backend, we are preparing to support native delta write in Spark 3.5 and delta 3.2, WriteFile is directly added on top of delta logical plan and hence the root SparkPlan is ColumnarWriteFilesExec which casue internal error without this change.

Other refactor

1. Using org.apache.spark.sql.catalyst.util.sideBySide to ouptput changed plan, which is same as spark RuleExecutor.
2. Improving some readability, case _ if !plan.supportsColumnar => case _ if plan.supportsColumnar
3. Adding comments for CHBatch.fromRow

(Fixes: #6705)

How was this patch tested?

Existed UTs