Fix sort in insert-lazy-install-configuration

Commit 1c4f685b13 replaced
configuration-layer--layers (a list of cfgl-layer objects) with
configuration-layer--used-layers (a list of symbols).  It also changed the
configuration-layer/insert-lazy-install-configuration function to use the
new variable, but it did not change the sort predicate.  Consequently, the
function started failing:

    Wrong type argument: listp, spacemacs-purpose

In addition, because sort is destructive, the function also deleted values
from configuration-layer--used-layers.

This commit fixes the sort predicate so that the function returns the
correct value, and it copies the list before sorting to avoid modifying
configuration-layer--used-layers.

* core/core-configuration-layer.el
(configuration-layer/insert-lazy-install-configuration): Use string<
as the sort predicate, and give sort a copy of the list.

CHANGELOG.develop

@@ -497,6 +497,8 @@ Other:
     to Sylvain Benner)
   - New function =configuration-layer/load-file= to load files silently (thanks
     to Sylvain Benner)
+  - Fix configuration-layer/insert-lazy-install-configuration, which has been
+    broken since v0.200.0.
   - Fixed duplicate "Open quick help..." in the minibuffer at startup (thanks to
     Sylvain Benner)
   - Fixed overflow of line in page-break-lines-mode when using line number

core/core-configuration-layer.el

@@ -2421,10 +2421,7 @@ depends on it."
   (let ((layer-name
          (intern (completing-read
                   "Choose a used layer"
-                  (sort configuration-layer--used-layers
-                        (lambda (x y)
-                          (string< (oref (cdr x) :name)
-                                   (oref (cdr y) :name))))))))
+                  (sort (copy-list configuration-layer--used-layers) #'string<)))))
     (let ((mode-exts (configuration-layer//lazy-install-extensions-for-layer
                       layer-name)))
       (dolist (x mode-exts)