Tracking issue: codegen dev experience improvements

[teh-cmc]

• IDL definition of an archetype must contain nothing but components #2372
• Automatically derive nullable if not attr.rerun.component_required #2373
• Exclude mock archetypes/datatypes/components from release artifacts #2537
• Do not require order attribute in trivially correct cases #2633
• Detect usage of required and panic with helpful message #2634
• Make source_hash.txt self-documenting #2636
• Parse default values during semantic pass #2641
• All components should implement From<InnerDatatype> in Rust backend #2675
• Detect and prevent re-used order attributes in same context #2680
• Bake Into<Cow> semantics into re_types::Loggable itself #2755
• Don't inline recursive datatypes, defer a runtime call to the child type instead #2759
• Automatically derive trivial From impls in Rust backend #2771

[teh-cmc]

This issue is specifically for tracking things that make would working with the codegen tools themselves easier, not the resulting generated code!