Fix memory leak for global module objects (Bug#42482).

Fix memory leak for global module objects (Bug#42482).

Instead of storing the global values in a global 'emacs_value_storage'
object, store them as hash values alongside the reference counts.
That way the garbage collector takes care of cleaning them up.

* src/emacs-module.c (global_storage): Remove.
(struct module_global_reference): New pseudovector type.
(XMODULE_GLOBAL_REFERENCE): New helper function.
(module_make_global_ref, module_free_global_ref): Use
'module_global_reference' struct for global reference values.
(value_to_lisp, module_handle_nonlocal_exit): Adapt to deletion of
'global_storage'.