## What changes were proposed in this pull request?
This change is a cleanup and consolidation of 3 areas related to Pandas UDFs:
1) `ArrowStreamPandasSerializer` now inherits from `ArrowStreamSerializer` and uses the base class `dump_stream`, `load_stream` to create Arrow reader/writer and send Arrow record batches. `ArrowStreamPandasSerializer` makes the conversions to/from Pandas and converts to Arrow record batch iterators. This change removed duplicated creation of Arrow readers/writers.
2) `createDataFrame` with Arrow now uses `ArrowStreamPandasSerializer` instead of doing its own conversions from Pandas to Arrow and sending record batches through `ArrowStreamSerializer`.
3) Grouped Map UDFs now reuse existing logic in `ArrowStreamPandasSerializer` to send Pandas DataFrame results as a `StructType` instead of separating each column from the DataFrame. This makes the code a little more consistent with the Python worker, but does require that the returned StructType column is flattened out in `FlatMapGroupsInPandasExec` in Scala.
## How was this patch tested?
Existing tests and ran tests with pyarrow 0.12.0
Closes#24095 from BryanCutler/arrow-refactor-cleanup-UDFs.
Authored-by: Bryan Cutler <cutlerb@gmail.com>
Signed-off-by: Hyukjin Kwon <gurwls223@apache.org>
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