Benchmarks do not compile

[cache-nez]

The project has been upgraded to Scala 3 but the benchmarks are still in Scala 2.12 (in particular, parseback-core and parseback-cats dependencies are available in Scala 2.12 at the latest; it is possible to upgrade other dependencies to Scala 2.13 or Scala 3) which is incompatible.

[vkuncak]

PRs to do this upgrade at least partially are welcome.

[redelmann]

The dependencies on parseback were for performance comparison purposes. Those benchmarks are not directly about Scallion and can thus be thrown out. The same might apply to other benchmarks.