[Notifications] Add a Mentions tab (#7044)

* Split out NotificationsTab

* Remove unused route parameter

* Refine the split between components

* Hoist some logic out of NotificationFeed

* Remove unused option

* Add all|conversations to query, hardcode "all"

* Add a Conversations tab

* Rename to Mentions

* Bump packages

* Rename fields

* Fix oopsie

* Simplify header

* Track active tab

* Fix types

* Separate logic for tabs

* Better border for first unread

* Highlight unread for all only

* Fix spinner races

* Fix fetchPage races

* Fix bottom bar border being obscured by glimmer

* Remember last tab within the session

* One tab at a time

* Fix TS

* Handle all RQKEY usages

* Nit

src/view/com/pager/Pager.tsx

@@ -136,12 +136,14 @@ export const Pager = forwardRef<PagerRef, React.PropsWithChildren<Props>>(
 
     return (
       <View testID={testID} style={[a.flex_1, native(a.overflow_hidden)]}>
-        {renderTabBar({
-          selectedPage,
-          onSelect: onTabBarSelect,
-          dragProgress,
-          dragState,
-        })}
+        <View style={a.z_10 /* Let tabbar bottom border cover the glimmer */}>
+          {renderTabBar({
+            selectedPage,
+            onSelect: onTabBarSelect,
+            dragProgress,
+            dragState,
+          })}
+        </View>
         <GestureDetector gesture={nativeGesture}>
           <AnimatedPagerView
             ref={pagerView}