test: fix a few issues in TestLengthFieldBasedFrameCodecZeroPlayLoad

Updates panjf2000#113

trifle: rename functions and refine comments

fix: resolve the issue of closing one fd twice

opt: Leverage system calls instead of `net` package to create listeners

Also enable SO_REUSEPORT to avoid Thundering Herd, besides, Fixes panjf2000#47 panjf2000#44 panjf2000#77

opt: avoid redundant calls to ResetBuffer()

fix: supplement all the formal protocol formats of TCP and UDP

opt: improve the implementation of Least-Connections load-balancing

Leverage min-heap to optimize Least-Connections load-balancing

mod: upgrade dependent modules

trifle: use more formal flags for eventfd

opt: improve the creation processes of netpoller

Fixes panjf2000#72