I was debugging [an issue] recently where it appears that the underlying
cause was a discrepancy in the size/align of a WIT type between Wasmtime
and `wit-parser`. This commit adds compile-time assertions that the size
of a WIT type is the same with `wit-parser` as it is in Wasmtime since
the two have different systems to calculate the size of a type. The hope
is that this will head off any future issues if they crop up.
[an issue]: https://github.com/bytecodealliance/wit-bindgen/issues/526
8a08fedc69