fix: adjust trampoline close_handles invalid to be safer (#6792)
## Summary
Closes https://github.com/astral-sh/uv/issues/6699
On cases like the ones described in
https://github.com/astral-sh/uv/issues/6699, `lpReserved2` somehow seems
to report multiple file descriptors that were not tied to any valid
handles. The previous implementation was faulting as it would try to
dereference these invalid handles. This change moves to using `HANDLE`
directly and check if its is_invalid instead before attempting to close
them.
## Test Plan
Manually tested and verified using `busybox-w32` like described in the
issue.
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Co-authored-by: konstin <konstin@mailbox.org>
