• Generate all the usual code for them (although without needing an actual IDL definition)
  Need a GenericIndicator(fqname: String) kinda thing to make it easy to build custom indicator components.
• Return them as part of the as_component_lists machinery
• Remove the codegen for Archetype::try_to_arrow, the default impl will now do everything needed

Requires #3103

TODO:

• First-class citizenry for indicator components - Rust #3252
• First-class citizenry for indicator components - Python #3253
• First-class citizenry for indicator components - C++ #3255