Implement a first version

Goals:

• Working macro
• Supports a language parameter
• Supports a layout parameter with same values as the code macro (for easy migrations)
• Supports both inline and standalone
• Support a source parameter with the same values as the code macro (for easy migrations)

Optional:

• Provide a code macro that replaces the standard XS code macro (to provide better performance without breaking backward compatibility)
• In the future, plug this macro as a code macro implementation, see https://forum.xwiki.org/t/change-the-code-macro-implementation/13308