[llvm-jitlink] Add diagnostic output and port executor to getaddrinfo(3) as well

Add diagnostic output for TCP connections on both sides, llvm-jitlink and llvm-jitlink-executor.
Port the executor to use getaddrinfo(3) as well. This makes the code more symmetric and seems to be the recommended way for implementing the server side.

Reviewed By: rzurob

Differential Revision: https://reviews.llvm.org/D98581