Restore public interfaces for accessing built-in package info

These functions were removed in ab36f58922
during the reorganization of package.el as part of Bug#80079.

Also add a simple test for these functions to avoid future regressions.

See also discussion at
https://lists.gnu.org/archive/html/emacs-devel/2026-06/msg00149.html.

* lisp/emacs-lisp/package.el (package-versioned-builtin-packages,
package-builtin-package-version): Restore.
* lisp/emacs-lisp/package-activate.el: Remove lingering comments.
* test/lisp/emacs-lisp/package-tests.el
(package-test-builtin-package-info): Add.

lisp/emacs-lisp/package-activate.el

@@ -208,8 +208,6 @@ called via `package-activate-all'.  To change which packages are
 loaded and/or activated, customize `package-load-list'.")
 (put 'package-alist 'risky-local-variable t)
 
-;;;; Public interfaces for accessing built-in package info
-
 ;;;###autoload
 (defvar package-activated-list nil
   ;; FIXME: This should implicitly include all builtin packages.

lisp/emacs-lisp/package.el

@@ -534,6 +534,22 @@ package."
   reqs
   summary)
 
+
+;;; Public interfaces for accessing built-in package info
+
+(defun package-versioned-builtin-packages ()
+  "Return a list of all the versioned built-in packages.
+The return value is a list of names of built-in packages represented as
+symbols."
+  (mapcar #'car package--builtin-versions))
+
+(defun package-builtin-package-version (package)
+  "Return the version of a built-in PACKAGE given by its symbol.
+The return value is a list of integers representing the version of
+PACKAGE, in the format returned by `version-to-list', or nil if the
+package is built-in but has no version or is not a built-in package."
+  (alist-get package package--builtin-versions))
+
 
 ;;; Installed packages
 

test/lisp/emacs-lisp/package-tests.el

@@ -1028,6 +1028,17 @@ but with a different end of line convention (bug#48137)."
             (list new-pkg-desc simple-depend-desc-2 simple-depend-desc-1
                   multi-file-desc simple-depend-desc simple-single-desc)))))
 
+(ert-deftest package-test-builtin-package-info ()
+  "Test public interfaces for querying package info."
+  (should (not (null (package-versioned-builtin-packages))))
+  ;; Picking any built-in library to check the version. Update results
+  ;; as needed.
+  (require 'lisp-mnt)
+  (should (equal (package-builtin-package-version 'cl-lib)
+                 (with-temp-buffer
+                   (insert-file-contents (locate-library "cl-lib.el"))
+                   (version-to-list (lm-version))))))
+
 (provide 'package-test)
 
 ;;; package-tests.el ends here