Implement Wasm proposal: non-trapping-float-to-int-conversions

[Robbepop]

This is about adding support for the non-trapping-float-to-int-conversions Wasm proposal.

The non-trapping-float-to-int-conversions Wasm proposal has already been included into the Wasm standard and is fairly light weight, therefore implementing it won't be a lot of work.

We should generally keep up with supporting finished Wasm proposals as this allows us to keep the Wasm spec test suite up to date.