* Refactor streaming signatureV4 w/ state machine
- Used state machine to make transitions between reading chunk header,
chunk data and trailer explicit.
* debug: add print/panic statements to gather more info on CI failure
* Persist lastChunk status between Read() on ChunkReader
... remove panic() which was added as interim aid for debugging.
* Add unit-tests to cover v4 streaming signature
Harshavardhana
kannappanr
Krishnan Parthasarathi