Cross build to Scala 3

[julien-truffaut]

The main issue is that macros are not compatible. We'll need to use the macro system, either in core or in a new macro3 module.

Per module:

• core Cross build core module to Scala 3  #925
• macro Create new macro module for Scala 3 #927
• refined

[julien-truffaut]

Maybe an intermediate milestone could be to cross build the core module

[cquiroz]

I'd love to contribute, do you think this can be split in a few tasks?

[julien-truffaut]

I'd love to contribute, do you think this can be split in a few tasks?

Yeah maybe one per module, what do you think?

[julien-truffaut]

@cquiroz I created a few issues and linked them to this ticket. I think it is best to start with core.