Replace synchronized blocks in retrofit2 with ReentrantLock(Improve)

[ChangguHan]

Motivation:

• Replace synchronized blocks in retrofit2 for Virtual Thread
• This is improvement of #4610

Modifications:

• remove synchronized in ArmeriaCallFactory's createRequest() by using CAS
• Add comments related to buffer's synchronized blocks.

Result:

• Remove synchronized block in retrofit2, but still have one issue with PipeBuffer(needed okhttp4)