windows: add functions to get named pipe process IDs

Fixes https://github.com/golang/go/issues/70086

Change-Id: I0cd188f075490b1ea630b26b74aa201796d60d3a
GitHub-Last-Rev: 498fe730f26f7766414913f6c21440c5f078b4c6
GitHub-Pull-Request: golang/sys#235
Reviewed-on: https://go-review.googlesource.com/c/sys/+/626215
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Reviewed-by: Quim Muntal <quimmuntal@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Ian Lance Taylor <iant@google.com>