Make number representations compatible with Wasm

[OlivierNicole]

This is best reviewed commit by commit. It adds a number of missing conversions, and other changes that have been performed in Wasm_of_ocaml in order to expose number-manipulating functions that are compatible with both the JS and Wasm backends.

This is part of a series of PRs intending to reduce the diff between js_of_ocaml and wasm_of_ocaml.

[hhugo]

Thanks. Looks good. Can you fix the CI and squash the fixup ?

[OlivierNicole]

Done. It looks like the failing test will only work if I integrate the single commit from #1650, which redefines Js.number_t as being Js.number Js.t.

This may break programs that do not perform explicit float conversions yet.

[hhugo]

Done. It looks like the failing test will only work if I integrate the single commit from #1650, which redefines Js.number_t as being Js.number Js.t.

This may break programs that do not perform explicit float conversions yet.

I removed the last commit, and fixed the hypertree example to use number_t

[OlivierNicole]

Thank you