Preserve the Windows `GetLastError` error in `HandleOrInvalid`.
In the `TryFrom<HandleOrInvalid> for OwnedHandle` and
`TryFrom<HandleOrNull> for OwnedHandle` implemenations, `forget` the
owned handle on the error path, to avoid calling `CloseHandle` on an
invalid handle. It's harmless, except that it may overwrite the
thread's `GetLastError` error.
r? `@joshtriplett`