feat: add Dart generation capability

[leomos]

What kind of change does this PR introduce?

Feature

What is the current behavior?

Dart types generation is not supported

What is the new behavior?

Dart types generation is supported

Additional context

• Test is failing, cannot figure out the problem for the life of me since there is no real and visible mismatch between the snapshot and the generated code; maybe some invisible character?
• Not a Dart expert, I expect some patterns might be improved
• Not a TypeScript expert either ( 😄 ) so the generation code is slightly different from the other generators and it works by creating a TypeScript object for each dart type (DartType interface) that is going to be eventually declared (Declarable interface); this was done mostly to wrap my head around the whole generation logic
• It supports most builtin types, enums, tables, views, composite types and lists of all of those (apart from views)
• It does not support materialized views