path/filepath: replace os.MkdirTemp with T.TempDir
Add the tempDirCanonical function, for tests that need a temporary
directory that does not contain symlinks.
Updates #45402
Change-Id: I3d08ef32ef911331544acce3d7d013b4c3382960
Reviewed-on: https://go-review.googlesource.com/c/go/+/308011
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Go Bot <gobot@golang.org> Reviewed-by: Ian Lance Taylor <iant@golang.org> Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>