Add test case in _demo/go/maphash to verify hash/maphash functionality with the new runtime.rand and runtime.memhash support. Generated with [codeagent](https://github.com/qbox/codeagent) Co-authored-by: luoliwoshang <luoliwoshang@users.noreply.github.com> Co-authored-by: xgopilot <noreply@goplus.org>