MDL-82055 output: replace usage of named templatable interface.

It's not available during, and breaks, site installation. The output
class doesn't necessarily need it in 78db6bb, so switch to simple
templatable interface instead.

Author: paulholden

.upgradenotes/MDL-81597-2024052802370704.yml

@@ -1,5 +1,5 @@
 issueNumber: MDL-81597
 notes:
   theme:
-    - message: New `core/contextheader` mustache template has been added. This template can be overridden by themes to modify the context header
+    - message: New `core/context_header` mustache template has been added. This template can be overridden by themes to modify the context header
       type: improved

lib/outputcomponents.php

@@ -26,8 +26,7 @@
  * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
 
- use core\output\local\action_menu\subpanel;
- use core\output\named_templatable;
+use core\output\local\action_menu\subpanel;
 
 defined('MOODLE_INTERNAL') || die();
 
@@ -4110,7 +4109,7 @@ public function export_for_template(renderer_base $output) {
  * @copyright 2015 Adrian Greeve <[email protected]>
  * @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  */
-class context_header implements renderable, named_templatable {
+class context_header implements renderable, templatable {
 
     /**
      * @var string $heading Main heading.
@@ -4232,16 +4231,6 @@ public function export_for_template(renderer_base $output): array {
             'additionalbuttons' => $additionalbuttons ?? [],
         ];
     }
-
-    /**
-     * Get the template name.
-     *
-     * @param renderer_base $renderer Renderer.
-     * @return string
-     */
-    public function get_template_name(renderer_base $renderer): string {
-        return 'core/contextheader';
-    }
 }
 
 /**

lib/templates/contextheader.mustache lib/templates/context_header.mustache

@@ -15,7 +15,7 @@
     along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
 }}
 {{!
-    @template core/contextheader
+    @template core/context_header
 
     Context header template.