refactor: Include the Eirini, EiriniX and Bits templates in KubeCF

[jandubois]

This PR moves the bits-service, eirini, and eirini-extensions subcharts from chart/charts/ to mixins/ and integrates them with the rest of kubecf. All subchart properties have been moved from e.g. .Values to .Values.bits etc. so that user overrides remain backwards compatible, even though the templates no longer reside in a subchart.

The long term goal is to have only the parts derived from cf-deployment in charts/ and both add-ons (like autoscaler), and native release (like UAA) as separate modules under mixins.

Parts of the subcharts that are completely unused by kubecf have been removed. Same thing for some configuration options that need to be hardcoded for kubecf.

The refactoring is not completely finished, but everything is working right now, including cf ssh, so to unblock other Eirini-related work this PR should be reviewed/merged now and remaining work done in a followup PR.

Fixes #1119
Fixes #1179
Fixes #1207

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Followup work (create separate Github issues before closing this PR):

• Create a tool to merge values.yaml (and values.schema.yaml) files from mixins into chart/values.yaml etc.
• Create a filechecker tool to verify that all filenames between the main chart and all mixins are unique and not overwrite each other while merging. Also verify that all templates/*.yaml file start with a line that calls _config.load.
• Determine mixin properties that should be exposed in values.yaml and move them back there.
• Provide more shared support for mixins, like managing of image references, configuring labels, taints, annotations, resource limits, etc.
• central versions for images
• reduced permissions for eirinix serviceaccount
• don't hardcode BITS_SERVICE_SIGNING_USER_PASSWORD
• detailed schema for mixins