Integrate build for Spark 3.2.3

This build integrates pre-built binaries for Spark 3.2.3.

Bug fixes and performance improvements

Configuration changes:

• Renamed shuffle manager to from org.apache.spark.shuffle.S3ShuffleManager to org.apache.spark.shuffle.sort.S3ShuffleManager.

Bugfixes:

• Fixed issue in serialized shuffle which prevent TeraSort to work properly.
• Fixed off-by-one error in by-pass shuffle-block-manager (thanks to @fhalde).

Improvements:

• This plugin now relies on S3ShuffleDataIO to write the shuffle output to the target location.
• Created the optional interface createSingleFileMapOutputWriter for the S3ShuffleDataIO component. This improved performance when Spark is able to write a shuffle-file without spilling.
• Removed S3SortShuffleWriter and S3BypassMergeSortShuffleWriter since these classes replicated already existing features.

Deprecated options

• spark.shuffle.s3.forceBypassMergeSort
• spark.shuffle.s3.allowSerializedShuffle
• spark.shuffle.s3.sort.cloneRecords

CI:

• Use travis to build releases.
• Added Spark 3.3.2 as a build target.

Release version 0.5

Changes from the initial open-source release:

• Refactored the scala classes from the sort into the shuffle package: SparkS3Shuffle needs to be activated with

   --conf spark.shuffle.manager="org.apache.spark.shuffle.S3ShuffleManager"
   --conf spark.shuffle.sort.io.plugin.class="org.apache.spark.shuffle.S3ShuffleDataIO"
  

• Creation of an io plugin class so that we are able to leverage more of the Spark Shuffle infrastructure
• Integration of SerializedShuffle (can be disabled with spark.shuffle.s3.allowSerializedShuffle)
• Added flag spark.shuffle.s3.sort.cloneRecords which copies Array[_] Key/value pairs in SortShuffle before insertion into the Spark ExternalSorter.
• Migrated from maven to sbt.
• Github Actions creates builds for Spark 3.2.0, 3.2.1 and 3.3.0 for both Scala 2.12 and 2.13.
• Added additional tests for Sort Shuffle.

Initial release with SortShuffle fix.

v0.4

CI: Fix version in build. (#5)