Implement the allowedRoutes.RouteNamespaces filters, which instruct
listens to only accept routes in a specific set of namespaces.

Remove --watch-namespaces from the test arguments, to allow tests that
create additional namespaces beyond their standard test namespace.

Merge the allowedRoutes configuration for Gateway listeners into the
generated managed Gateway listeners. If a user listen has the same
protocol as a generated listener, add the user listener's allowedRoutes
section into the generated listener.

When looking for a supported gateway, only check the listeners whose
protocol matches the route type.

Check that AllowedRoutes from user-provided Listeners meet the criteria
necessary for Kong: Listeners for the same protocol must not specify
different filter requirements because Kong combines all routes into a
single proxy configuration.

Co-authored-by: Shane Utt <shaneutt@linux.com>