MDL-55564 core_admin: Convert admin settings to use templates

Part of MDL-55071

admin/templates/setting.mustache

@@ -0,0 +1,43 @@
+{{!
+    This file is part of Moodle - http://moodle.org/
+
+    Moodle is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    Moodle is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
+}}
+{{!
+    Setting.
+}}
+<div class="form-item clearfix" id="{{id}}">
+    <div class="form-label">
+        <label {{#labelfor}}for="{{labelfor}}"{{/labelfor}}>
+            {{{title}}}
+            {{#override}}
+                <div class="form-overridden">{{override}}</div>
+            {{/override}}
+            {{#warning}}
+                <div class="form-warning">{{warning}}</div>
+            {{/warning}}
+        </label>
+        <span class="form-shortname">{{{name}}}</span>
+    </div>
+    <div class="form-setting">
+        {{#error}}
+            <div><span class="error">{{error}}</span></div>
+        {{/error}}
+        {{{element}}}
+        {{#default}}
+            <div class="form-defaultinfo">{{{default}}}</div>
+        {{/default}}
+    </div>
+    <div class="form-description">{{{description}}}</div>
+</div>