Remove shadowing of gRPC and netty #671
Description
Bug Report
1. Describe the bug
We previously added some metrics into gRPC and netty, and introduced some shadowing files to https://github.com/tikv/client-java/tree/master/src/main/java/io. While upgrading the gRPC/netty, might be painful and can present subtle bugs because of the binary compatibility. We might remove the shadowing code and consider a less invasive way to observe the gRPC/netty.