Prepare scala-cli to handle Scala 3 Native correctly

[jchyb]

This includes a couple of changes:

• Similarly to a regular Scala or Scala.js, a scala3-library is fetched if Scala 3 is used (here called scala3lib for Native)
• Scala Native compatibility checks were updated - now everything is checked against both Scala language version and Scala Native version. The error message was also adjusted.
• If a snapshot version of scala-native-cli is used, now a Sonatype snapshot repository should be also checked for it. This is something I did not take into consideration before, and while up to this point no snapshot version of scala-native-cli was released, this is more of a future-proof than necessary change.

I was testing it with a locally published scala-native-cli 0.4.3-SNAPSHOT and scala-native-cli 0.4.3-RC2 should be released soon. On that release I'll add additional Scala 3 Native integration tests to the CI (either in this PR or separately, however will be more convenient)

[jchyb]

I want to add some tests, I will add them and mark this PR as ready after the scala-native 0.4.2-RC2 release

[WojciechMazur]

Scala Native CLI artifacts for 0.4.3-RC2 were published today

[romanowski]

There is one nit I found but this is not that important.

I think the documentation needs to be updated since e.g. our Scala Native guide mentions Scala versions.