Check that `Size::check` fails for large sizes on 16 and 32 bit platforms

It must be possible to convert `Size` values to `usize` values. Thus, if a `Size` would overflow a `usize`, `Size::check` should return an error.

`Size` is currently represented as a `U64`, so `Size::check` will always succeed on 64 bit platforms. However, conversions could fail on 16 bit and 32 bit platforms.

Figure out a way to test the conversions on these platforms. Ideally via CI. I should also check that types containing an invalid `Size` also fail.