implicit-dynamic: false, anonymous functions, and explicitly dynamic types require gratuitous verbosity in code

Supporting the generation of code that's compliant with `implicit-dynamic: false` is is a BIG request for json_serializable

https://github.com/dart-lang/json_serializable/issues/557

The VAST majority of the cases in generate code map to something like this

image.png

error: Missing parameter type for 'e'. (implicit_dynamic_parameter at [json_serializable] test/kitchen_sink/kitchen_sink.g_exclude_null__non_nullable.g.dart:117)

`e` in this case maps back to something explicitly dynamic. Adding explicit `dynamic` here seems silly and redundant.

Is there some deeper logic here I'm missing? Could we update this error?