du: Reuse metadata from DirEntry where possible

[jesseschalken]

On Windows, the DirEntry object has metadata already loaded, so calling dir_entry.metadata() instead of fs::symlink_metadata(path) saves a syscall.

~1.29x speedup on my test directory.

Before

> cargo build --release
> measure-command { .\target\release\coreutils.exe du --apparent-size "test folder" }
TotalSeconds      : 12.0716311

After

> cargo build --release
> measure-command { .\target\release\coreutils.exe du --apparent-size "test folder" }
TotalSeconds      : 9.3127479

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/rm/rm1 (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/tail/inotify-dir-recreate (fails in this run but passes in the 'main' branch)

[cakebaker]

Thanks for your PR :)