Avoid closing invalid handles
Documentation for [`HandleOrInvalid`] has this note:
> If holds a handle other than `INVALID_HANDLE_VALUE`, it will close the handle on drop.
Documentation for [`HandleOrNull`] has this note:
> If this holds a non-null handle, it will close the handle on drop.
Currently, both will call `CloseHandle` on their invalid handles as a result of using `OwnedHandle` internally, contradicting the above paragraphs. This PR adds destructors that match the documentation.
```@rustbot``` label A-io O-windows T-libs
[`HandleOrInvalid`]: https://doc.rust-lang.org/std/os/windows/io/struct.HandleOrInvalid.html
[`HandleOrNull`]: https://doc.rust-lang.org/std/os/windows/io/struct.HandleOrNull.html
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