This commit adds a method, `Module::initialize_copy_on_write_image`,
which will explicitly create the copy-on-write image during the method
call instead of lazily deferring it until the first instantiation of a
module. Given the relative expense of creation of a memfd on Linux this
can otherwise run the risk of unnaturally perturbing the
time-of-instantiation of a module. Additionally whenever lazy
initialization is provided in an API it's typically good practice to
also have an optionally-called forced initialization.
7e8f356798