Why does the flushPendingResponse method have no backpressure? #4663
Description
BUG REPORT
Describe the bug
like org.apache.bookkeeper.proto.PacketProcessorBase#sendResponse, if the client is unable to process in time, use Netty high water level control to avoid FullGC or OOM
Expected behavior
org.apache.bookkeeper.proto.BookieRequestHandler#flushPendingResponse method supports backpressure
Additional context
bookkeeper-4.17