* implemented Source unit for S3.
Implemented. integration test
* use bucket as source unit
* remove code duplication, reuse from Chunks
* remove unnecessary change
* remove unused functions
* revisit tests
* revert unnecessary change
* change SourceUnitKind to s3_bucket
* handle nil objectCount inside scanBucket
* handle nil objectCount outside loop
* add bucket to resume log
* add bucket and role to error log, remove enumerating log
* implement sub unit resumption
* add comment to checkpointer for unit scans
* implement SourceUnitUnmarshaller on source with the new S3SourceUnit, add test to test resumption on multiple buckets with concurrent ChunkUnit processing
* add role to SourceUnitID
* Revert "add role to SourceUnitID"
This reverts commit 549e6bede9fe4ed276f7a23f5a5b2bf037133264.
* add role to source unit ID, keep track of resumption using source unit ID instead of just bucket name
* rename bucket -> unitID in UnmarshalSourceUnit
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Co-authored-by: Amaan Ullah <[email protected]>
