Using macros insted build_runner

[TheLastFlame]

It's been a day since the test implementation of macros was introduced, but there is still no issue with a suggestion to use them.

Perhaps it is not optimal to develop an implementation based on them before the macros api is released in stable.
But I am creating this issue to be able to keep track of updates on this topic.

[rrousselGit]

There's already an issue and I already closed it ;)

As I said in the other issue:
Macros are lacking too many features to post Freezed as is (they are still in implementation)

I'm working on some stuffs, with workarounds and stuff. We'll see.
But there's not really a point in having this issue around for now.