Fixes; allow built_collection 4; ignore unnecessary_const/new
- Improve generation for operator==, don't use dynamic.
- Improve error message and documentation for missing builder factory.
- Allow built_collection 4.0.0.
- Fix code generation stack overflow when there is a loop in serializable types.
- Fix library name output in generation error messages.
- Add ignores for lints 'unnecessary_const' and 'unnecessary_new' to generated code.