recent view: Add button to fetch more conversations.

We add a new timerender format for this context, where there's plenty
of space.

Fixes: #18461

web/tests/message_fetch.test.js

@@ -28,6 +28,7 @@ mock_esm("../src/recent_view_ui", {
     process_messages: noop,
     show_loading_indicator: noop,
     hide_loading_indicator: noop,
+    set_oldest_message_date: noop,
 });
 mock_esm("../src/ui_report", {
     hide_error: noop,

web/tests/timerender.test.js

@@ -105,6 +105,12 @@ run_test("get_localized_date_or_time_for_format returns correct format", () => {
                 date: "Wed, Jan 27, 2021, 1:53 AM",
             },
         },
+        {
+            format: "full_weekday_dayofyear_year_time",
+            expected: {
+                date: "Wednesday, January 27, 2021 at 1:53 AM",
+            },
+        },
     ];
 
     for (const format of formats) {