subscription: Include archived channels in streams list.

`is_archived` field is added to the stream and types.

Include a new `archived_channeels` client capability, to allow clients
to access data on archived channels, without breaking
backwards-compatibility for existing clients that don't know how to
handle these.

Also, included `exclude_archived` parameter to `/get-streams`,
which defaults to `true` as basic clients may not be interested
in archived streams.

zerver/lib/home.py

@@ -156,6 +156,7 @@ def build_page_params_for_home_page_load(
         linkifier_url_template=True,
         user_list_incomplete=True,
         include_deactivated_groups=True,
+        archived_channels=False,
     )
 
     if user_profile is not None: