Merge: Runtime function

Refactor SeparateRuntimeFunction and related services in the separate compiler.

This simplify the compiler and improve the efficiency of the generated code a little.

Before: 0m7.588s
After: 0m7.364s (-3%)

This refactorisation is required for some next PR that will improve polymorphic calls

Pull-Request: #1102
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>
Reviewed-by: Lucas Bajolet <r4pass@hotmail.com>