Extract feed routes (#2269)

* Extract feed routes from invidious.cr
* Removes the deprecated route for /feed/top
* Deprecate /view_all_playlist & use /feed/playlists
* Move feed views into their own directory

* Add haltf method to halt current route context
* Change status_code + return blocks to use haltf

* Set appropriate response headers for RSS routes

src/invidious/views/playlist.ecr

@@ -12,7 +12,7 @@
         <% if playlist.is_a? InvidiousPlaylist %>
             <b>
                 <% if playlist.author == user.try &.email %>
-                <a href="/view_all_playlists"><%= author %></a> |
+                <a href="/feed/playlists"><%= author %></a> |
                 <% else %>
                 <%= author %> |
                 <% end %>

src/invidious/views/preferences.ecr

@@ -312,7 +312,7 @@
                 </div>
 
                 <div class="pure-control-group">
-                    <a href="/view_all_playlists"><%= translate(locale, "View all playlists") %></a>
+                    <a href="/feed/playlists"><%= translate(locale, "View all playlists") %></a>
                 </div>
 
                 <div class="pure-control-group">