Add (system finalizers)

This will replace an internal interface in (system foreign-objects).

* module/system/finalizers.scm: New file.
* am/bootstrap.am (SOURCES): Add new file.
* libguile/foreign-object.h:
* libguile/foreign-object.c (invoke_finalizer):
(sys_add_finalizer_x):
(scm_init_foreign_object):
(scm_register_foreign_object): Remove.
* libguile/init.c (scm_i_init_guile): Register finalizers instead of
foreign-object.
* module/system/foreign-object.scm (allocate-instance): Use finalizers
module.
* libguile/finalizers.c (invoke_finalizer):
(scm_sys_add_finalizer): New helper.

module/system/foreign-object.scm

@@ -1,6 +1,6 @@
 ;;; Wrapping foreign objects in Scheme
 
-;;; Copyright (C) 2014, 2015, 2024 Free Software Foundation, Inc.
+;;; Copyright (C) 2014, 2015, 2024, 2025 Free Software Foundation, Inc.
 ;;; 
 ;;; This library is free software; you can redistribute it and/or
 ;;; modify it under the terms of the GNU Lesser General Public
@@ -24,13 +24,10 @@
 
 (define-module (system foreign-object)
   #:use-module (oop goops)
+  #:use-module (system finalizers)
   #:export     (make-foreign-object-type
                 define-foreign-object-type))
 
-(eval-when (eval load expand)
-  (load-extension (string-append "libguile-" (effective-version))
-                  "scm_init_foreign_object"))
-
 (define-class <foreign-class> (<class>))
 
 (define-class <foreign-class-with-finalizer> (<foreign-class>)
@@ -42,7 +39,7 @@
   (let ((instance (next-method))
         (finalizer (finalizer class)))
     (when finalizer
-      (%add-finalizer! instance finalizer))
+      (add-finalizer! instance finalizer))
     instance))
 
 (define* (make-foreign-object-type name slots #:key finalizer