* Remove ability to create segments in v8 format
* Fix IndexGeneratorJobTest
* Fix parameterized test name in IndexMergerTest
* Remove extra legacy merging stuff
* Remove legacy serializer builders
* Remove ConciseBitmapIndexMergerTest and RoaringBitmapIndexMergerTest
* refactor lag reporting and report lag at status endpoint
* refactor offset reporting logic to fetch offsets periodically vs. at request time
* remove JavaCompatUtils
* code review changes
* code review changes
* Refactoring Appenderator
1) Added publishExecutor and handoffExecutor for background publishing and handing segments off
2) Change add() to not move segments out in it
* Address comments
1) Remove publishTimeout for KafkaIndexTask
2) Simplifying registerHandoff()
3) Add increamental handoff test
* Remove unused variable
* Add persist() to Appenderator and more tests for AppenderatorDriver
* Remove unused imports
* Fix strict build
* Address comments
* Fix lz4 library incompatibility in kafka-indexing-service extension #3266
* Bumped Kafka version to 0.10.2.0 for : Fix lz4 library incompatibility in kafka-indexing-service extension #3266
* Replaced Lists.newArrayList() with Collections.singletonList() For Fix lz4 library incompatibility in kafka-indexing-service extension #4115
* option to reset offset automatically in case of OffsetOutOfRangeException
if the next offset is less than the earliest available offset for that partition
* review comments
* refactoring
* refactor
* review comments
