…smBuilder.

This is in the context of making `WasmBuilder` closer to the JS
back-end `ClassEmitter` and `HelperFunctions` closer to `CoreJSLib`.
The former is responsible for the generation of everything that
relates to a given `LinkedClass`, while the latter is responsible
for generating everything that is more global.

We are going to give it the same kinds of responsibilities as
`CoreJSLib` for the JS back-end.

This corresponds to the JS backend, where all definitions that are
not related to any particular class are handled by `CoreJSLib`.

It now has the same responsibilities as the `ClassEmitter` in the
JS backend.

It has the same responsibilities as `Emitter` in the JS backend,
namely handling the macro-structure of the output files, but not
I/O operations.

This way, WasmContext is not responsible for emitting code anymore.
It only acts as a knowledge repository.