fix: Update windows to 0.54

[DataTriny]

The major highlight of this PR is that VariantFactory is replaced by a simpler Variant newtype. The VARIANT type from the windows crate is used directly whenever possible.

[mwcampbell]

@DataTriny Are you sure that calling HRESULT::from_win32 on UIA_E_ELEMENTNOTAVAILABLE and UIA_E_INVALIDOPERATION is correct? Those constants are already HRESULT codes, not Win32 errors. I guess we need tests that cover those errors.

[mwcampbell]

I think what we need to do is just directly construct the HRESULT struct, like this:

HRESULT(UIA_E_ELEMENTNOTAVAILABLE as _)

This is based on looking at how constants like windows::Win32::Foundation::E_NOTIMPL are written.

[DataTriny]

@mwcampbell I tried printing a debug representation of those errors and I think you're right.

[DataTriny]

I previously made sure that Error::empty() was equivalent to Error::OK.