Implementation of recycling memory pool.

[kidkun]

Add a new memory pool implementation in socket server.

This implementation is able to recycle the buffers of common request size(configurable via a new config, SocketRequestCommonBytes) to reuse the buffers for future request. Doing so can avoid many expense system call if the incoming requests` size are relatively fixed or distributed in normal distribution.

An example is like below,
received request1 of size1 byte -> allocate buffer for request 1
request 1 is processed by API layer -> instead of deallocate the buffer, clear it and save it in cache
received request2 of (size1- 100 byte) -> reuse the cached buffer for request 2 since request size is close and buffer is large enough

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[radai-rosenblatt]

sean is correct - lets drop down to something simpler (pre-allocated deque of the correct size) so we could measure impact on GC and decide on further optimizations later.

[radai-rosenblatt]

one last change requested :-)

[radai-rosenblatt]

failing unit test:
kafka.server.KafkaConfigTest > testFromPropsInvalid FAILED
org.scalatest.exceptions.TestFailedException: Expected exception java.lang.Exception to be thrown, but no exception was thrown
at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:530)
at org.scalatest.Assertions$.newAssertionFailedException(Assertions.scala:1389)
at org.scalatest.Assertions$class.intercept(Assertions.scala:824)
at org.scalatest.Assertions$.intercept(Assertions.scala:1389)