[ALL] Tailor schemas to render a lighter Onyxia interface

[Gaspi]

Description of the change

Modify values.schema.json files to provide a more readable Onyxia interface:

• Systematic titles rather than defaulting to the properties' name
• Explicit (but not too long) titles
• Non-redundant descriptions (do not repeat the title or elements inferrable from context)
• Avoid descriptions at all if the title can be descriptive enough

Checklist

• Chart version bumped in Chart.yaml
• Title of the pull request follows this pattern [name_of_the_chart] Descriptive title