Helm-apps role for installing helm charts (#8347)

* Sketch of helm-apps role interface

* helm-apps: Early implementation and settings

* helm-apps: Fix README.md example playbook

* fixup! Sketch of helm-apps role interface

* Make the argument specs more explicit

* Remove exposed options from hardcoded default

* Simplify example playbook in README.md

- Define directly the roles parameters
- Add an example of option override for one chart only

* Use release instead of charts

Make explicit that the role is mananing releases, not charts.
Simplify parameters naming