feat(ui): clear panel form inputs when closed

This commit replaces the SSH key-specific code in favor of resetting
panel forms when closed, which thus carries the same behavior over to
the GPG key field.

web_src/js/utils/dom.js

@@ -51,6 +51,14 @@ export function isElemHidden(el) {
   return res[0];
 }
 
+export function resetForms(el) {
+  queryElemChildren(el, 'form', resetForm);
+}
+
+function resetForm(form) {
+  form.reset();
+}
+
 function applyElemsCallback(elems, fn) {
   if (fn) {
     for (const el of elems) {