os: add os.ModeSocket support to os.Stat on windows
Unix sockets are identified by the IO_REPARSE_TAG_AF_UNIX reparse tag.
Teach fileStat.Mode() to recognize this tag and set the os.ModeSocket
bit in such case.
Note that there is a bug starting in Windows 19H1 until 20H1 that
makes the IO_REPARSE_TAG_AF_UNIX tag not being set for unix sockets.
This CL doesn't provide a workaround for this bug.
Fixes #33357.
Change-Id: Iea8f24b20672c8d4b03f55ef298d128431dc3fac
Reviewed-on: https://go-review.googlesource.com/c/go/+/561937
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Alex Brainman <alex.brainman@gmail.com> Reviewed-by: David Chase <drchase@google.com> Reviewed-by: Bryan Mills <bcmills@google.com>