support Catalyst chart defaults

As part of the new chart addition, entries in charts.yaml can now optionally specify a set of default, Catalyst-specific overrides. These defaults can be in turn overridden by clients, but they supersede chart defaults otherwise. This was necessary for the wikifunctions chart because Catalyst can't support AppArmor configurations at the moment and we didn't want to change the upstream default of the chart.

This MR also includes housekeeping to update versions, fix TODOs and other several improvements

Bug: T374864