[release-branch.go1.20] os: if descriptor is non-blocking, retain that in Fd method

[release-branch.go1.20] os: if descriptor is non-blocking, retain that in Fd method

For #58408
For #60211
Fixes #60217

Change-Id: I30f5678b46e15121865b19d1c0f82698493fad4e
Reviewed-on: https://go-review.googlesource.com/c/go/+/495079
Run-TryBot: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>
Run-TryBot: Ian Lance Taylor <iant@google.com>
(cherry picked from commit f777726ff073f8066c017649b572bd8c40940a42)
Reviewed-on: https://go-review.googlesource.com/c/go/+/496015
Reviewed-by: Heschi Kreinick <heschi@google.com>
Auto-Submit: Heschi Kreinick <heschi@google.com>