BP-39 Bookie checksum validation

**BP**

This is the master ticket for tracking **BP-39 Bookie checksum validation**

Bookkeeper client calculates the checksum for the data it receives from application as well as the header. Recently, we hit a data corruption issue and was root caused at the fact that the data received by bookies was corrupted before even it was persisted to disk. This is a potentially serious condition, since we could have written all the copies incorrectly. In such a case, there is no way to recover and auto heal, since the data is lost forever. As a storage system, we want to add a checksum check on the server side as well.

Proposal PR - [Link](https://docs.google.com/document/d/1K2-qoSblH5s2Ag4d5QahZZ7xT7kTH9dP_UX--YHKyIo/edit#)