path/filepath: re-implement windows EvalSymlinks

path/filepath: re-implement windows EvalSymlinks

CL 41834 used approach suggested by Raymond Chen in
https://blogs.msdn.microsoft.com/oldnewthing/20100212-00/?p=14963/
to implement os.Stat by getting Windows I/O manager
follow symbolic links.

Do the same for filepath.EvalSymlinks, when existing
strategy fails.

Updates #19922
Fixes #20506

Change-Id: I15f3d3a80256bae86ac4fb321fd8877e84d8834f
Reviewed-on: https://go-review.googlesource.com/55612
Reviewed-by: Ian Lance Taylor <iant@golang.org>