Rework printing of module functions

Rework printing of module functions

Fix a FIXME in emacs-module.c.  Put the printing into print.c, like
other types.

* src/print.c (print_vectorlike): Add code to print module functions.

* src/emacs-module.c (funcall_module): Stop calling
'module_format_fun_env'.  Now that module functions are first-class
objects, they can be added to signal data directly.
(module_handle_signal): Remove now-unused function
'module_format_fun_env'.

* test/src/emacs-module-tests.el (mod-test-sum-test): Adapt unit test.

* src/eval.c (funcall_lambda): Adapt call to changed signature of
'funcall_module'.