Adding ChunkManager implementation

[AnatolyPopov]

Adding ChunkManager implementation that allows to fetch a specific chunk and return as decrypted and decompressed stream of bytes.

[jeqo]

Thanks @AnatolyPopov.
I think we need some tests for this component as well.

Also, some general comments:
The getChunk implementation (decrypt, decompress) corresponds to the uploading logic (compress, encrypt). These should be on the same place.
I see two alternatives to do this:

• URSM implementing this interface
• Extending this class to handle all interaction between Kafka TS ops and ObjectStorageFactory:
  • In this case, I'd rename the class to ChunkedSegmentManager or similar, and extend it to fetchChunk, uploadSegment (including upload log, indexes, and manifest) and deleteSegment.

I'm leaning towards the second option. Though, regardless, agreeing on either should help to scope this and the following PRs better. wdyt?

[AnatolyPopov]

@jeqo I totally agree regarding regarding your comment about having encryption/decryption and compression/decompression in the same place and was thinking about refactoring but I believe this can be addressed in other PRs and requires some discussions. For now I would proceed almost as is to finally get the first version working and then refactor this.

[jeqo]

Sure, let's review it after URSM implementation is merged. Creating #207 to follow up.

[jeqo]

@AnatolyPopov could you squash commits? I can merge it right after

[AnatolyPopov]

@jeqo Done