Unnecessary copying bytes

[kezhenxu94]

• I have searched the issues of this repository and believe that this is not a duplicate.

Ⅰ. Issue Description

there are many operations like:

https://github.com/seata/seata/blob/b7a930d0528030caca53c811d740703e3f676e94/core/src/main/java/io/seata/core/rpc/netty/MessageCodecHandler.java#L80-L82

in class io.seata.core.rpc.netty.MessageCodecHandler, which copies the bytes over and over, and it can just be replaced with:

out.writeBytes(byteBuffer);

if it makes sense to you, I'll send a PR to fix this, thanks :)

Ⅲ. Describe what you expected to happen

no unnecessary copies

[slievrly]

@kezhenxu94 it makes sense.