Compaction must preserve commit timestamps of merged records

[bvaradar]

During Compaction, HoodieCompactedRecordScanner merges log records in log files and feeds them to MergeHandle. MergeHandle merges these records with the old columnar data (in base-file). While doing the second level merge, if the mergeHandle chooses the record coming from log, it re-tags hoodie metadata for that record with compaction commit time (using HoodieStorageWriter.writeAvroWithMetadata). For incremental pull, this could cause same update to be returned at different commits. Hence, we need to ensure commit-time for records appended to log-files gets preserved after compaction

[bvaradar]

@n3nash @vinothchandar : FYI

[vinothchandar]

Moved to https://issues.apache.org/jira/browse/HUDI-44