Django 3.x and higher require specifying an app name when also

specifying a namespace for include() when building URL patterns.

This change adds app_name to complement namespace in

build_integration_urlpatterns().
The function itself now expects keyword arguments. Positional arguments

are supported but deprecated with a warning.
Type hints have also been added throughout djblets.integrations.urls.

Made use of this with RBCommons, which needs this on Django 3.2.