admin users: Use plain HTML and static dates.

We want to avoid creating jQuery objects that just
get turned right back into strings by the list
widget, so we now have our template just include
`last_active_date` instead of kludging it in
after the fact, and we return the template
string in `modifier` rather than wrapping it.

To deal with plain HTML we switch to using
`render_now`.

Calling `render_now` leads to a more simple
codepath than `render_date`, beyond just dealing
with text.

The `render_date` function has special-case logic
that only applies to our time dividers in our
message view, which is why we were passing the
strange `undefined` parameter to it before this
fix.

The `render_date` function was also putting
the dates into `update_list` for once-a-day
updates, which is overkill for an admin screen.
We don't use this logic for drafts or attachments
either.  I'm not sure how well tested that logic
is, and it's prone to slow leaks.

This commit sets us up to simplify the list
widget not to have bit-rot-prone code related
to jQuery objects.

static/js/settings_users.js

@@ -197,28 +197,26 @@ function populate_users(realm_people_data) {
         },
     });
 
-    function get_rendered_last_activity(user) {
+    function get_last_active(user) {
         const last_active_date = presence.last_active_date(user.user_id);
 
         if (!last_active_date) {
-            return $("<span></span>").text(i18n.t("Unknown"));
+            return i18n.t("Unknown");
         }
-        const today = new XDate();
-        return timerender.render_date(last_active_date, undefined, today);
+        return timerender.render_now(last_active_date).time_str;
     }
 
     const $users_table = $("#admin_users_table");
     list_render.create($users_table, active_users, {
         name: "users_table_list",
         modifier: function (item) {
-            const $row = $(render_admin_user_list({
+            return render_admin_user_list({
                 can_modify: page_params.is_admin,
                 is_current_user: people.is_my_user_id(item.user_id),
                 display_email: settings_data.email_for_user_settings(item),
                 user: item,
-            }));
-            $row.find(".last_active").append(get_rendered_last_activity(item));
-            return $row;
+                last_active_date: get_last_active(item),
+            });
         },
         filter: {
             element: $users_table.closest(".settings-section").find(".search"),

static/templates/admin_user_list.hbs

@@ -37,6 +37,7 @@
     </td>
     {{else if is_active}}
     <td class="last_active">
+        {{ ../last_active_date }}
     </td>
     {{/if}}
     {{#if ../can_modify}}