This commit removes the currently existing laziness-via-`OnceCell` when
a `Module` is created for creating a `ModuleMemoryImages` data
structure. Processing of data is now already shifted to compile time for
the wasm module which means that creating a `ModuleMemoryImages` is
either cheap because the module is backed by a file on disk, it's a
single `write` into the kernel to a memfd, or it's cheap as it's not
supported. This should help make module instantiation time more
deterministic, even for the first instantiation of a module.
bc1170c2dd