[improve] Prevent memory copy and heap memory allocation when read entry

[dao-jun]

Motivation

Prevent memory copy when read entry.

Changes

(Describe: what changes you have made)

Master Issue: #

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[dao-jun]

@lhotari @eolivelli @hangc0276 @zymap Could you please take a look?

[hezhangjian]

I am not familiar with netty reference count. I have two questions.

1. why we need onSendResponseFinished? Can we just change to UnsafeByteOperations.unsafeWrap(entryBody.nioBuffer())? It may leak memory?
2. I think extract a class field is a little hard to maintenance, can we still pass it by method?

[dao-jun]

I am not familiar with netty reference count. I have two questions.

1. why we need onSendResponseFinished? Can we just change to UnsafeByteOperations.unsafeWrap(entryBody.nioBuffer())? It may leak memory?
2. I think extract a class field is a little hard to maintenance, can we still pass it by method?

@shoothzj

1. UnsafeByteOperations is protobuf‘s API, it will not release the memory, so we have to release it manually.
2. Pass body by method will lead to more changes, this is the most simple way.