Move default backend component into the deps folder

The default backend component only gets used when Nginx is providing the ingress. Migrate this object into chart/deps/harness-ingress-controller so that it does not get deployed as part of the chart.

Acceptance Criteria

• Move chart/templates/cg/default-backend/ to chart/deps/harness-ingress-controller/
• Test that the chart still functions
• Submit MR