std: fix compile error in std.fs.File.tryLock

[HydroH]

Contributes to #21094 .

Handles unlock case in windows. Returns true if the file is not locked; this aligns with the behavior of posix systems.

[Rexicon226]

See #21306 for a more lengthy discussion on fixing this compile error. You'll see that this fix isn't fully correct.

[HydroH]

See #21306 for a more lengthy discussion on fixing this compile error. You'll see that this fix isn't fully correct.

Thanks for your review, it seems I'm missing the implementations in lock().

But in the case of behavior, I suppose a function should have the same behavior on different OSs? std.fs.File.tryLock will not panic on POSIX systems when trying to unlock files that are not locked, so I think behavior on Windows should be similar; also unlocking a file that is not locked is certainly not a codepath that will never be executed, and should not cause undefined behaviors.