* Update to use the latest protobuf package to build pb

The pb package was generated some time ago with old version
of https://github.com/golang/protobuf which was deprecated
and in favor of google.golang.org/protobuf (see
deprecation notice in https://pkg.go.dev/github.com/golang/protobuf)

This PR updates the generation of pb package with
v1.27.1 of google.golang.org/protobuf.
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>

* Exclude pb from import test
Signed-off-by: Yong Tang <yong.tang.github@outlook.com>