feat(library): added <RenderChild> and <RenderChildren>

[GauBen]

Description

• Added <RenderChild name="child" /> to render the child if found, add content buttons otherwise
• Added <RenderChildren> to render all/subset/filtered children, add content buttons afterwards
• Deprecated <Area asSubNode />

Checklist

Source code

• I've considered the implications on security (in particular for changes to authentication, authorization, data fetching, ...)
• I've considered the implications on performances
• I've considered the implications on migration
• I've considered the implications on code maintainability

Tests

• I've provided Unit and/or Integration Tests
• I've updated the parent issue with required manual validations

Documentation

• I've provided inline documentation (Source code)
• I've provided internal documentation (README, Confluence)
• I've provided user-facing documentation (Academy)

Tip

Documentation to guide the reviews: How to do a code review