Support primary constructors

[donny-dont]

Change the check for the _ value constructor to support new _().

[donny-dont]

The check for the factory constructor works with the primary constructor feature of dart 3.13 out of the box so just targeting the _ constructor.

[davidmorgan]

Thanks! I will take a look, probably there is additional work that is useful with this.

[donny-dont]

@davidmorgan is there anything I can do to move things along? Without this change anyone trying to use built value classes cannot update to the new primary constructor format. The generator will refuse to accept the new syntax as being valid.

[davidmorgan]

@donny-dont commenting here is a good way :) I'll try to get to it this week. Thanks :)

[donny-dont]

@davidmorgan sounds good!

I don't know what Dart SDK's this is tested against but if its sdk: ^3.13 then I could bump the internal end to end examples to that and then write a test that uses the primary constructors. I did notice that the examples used older versions of some dart packages like having pedantic instead of lints. Might be a good excuse to bump those to use more recent Dart language features.

[donny-dont]

Looks like you've got this covered in #1400 so I'm going to close this and let you do your thing! Thanks for getting this figured out!