Do we need source_gen/builder.dart?

[matanlurey]

It seems confusing since it's also exported through source_gen.dart.

Can we deprecate/remove?

[kevmoo]

CC @jakemac53 @natebosch

[jakemac53]

We probably don't need it - no (obviously a breaking change to remove it though so I would just deprecate it until the next breaking release?). I don't think its work a breaking release on its own.