Upgrade all crates to syn2

[Dav1dde]

We still have derive crates depending on syn v1, the eco-system is moving on and more and more dependencies we also use in the derive crates now require syn v2.

With #4307 we now have to ignore lints in generated code because we cannot update the dependency since we still need syn v1.

Biggest hurdle seems to be usage of parse_meta(), this SO question could be useful.