Use compileOnly configuration for optional language dependencies

[knutwannheden]

What problem are you trying to solve?

Currently, the rewrite-static-analysis has runtime dependencies on language bindings like rewrite-csharp and rewrite-kotlin (more to follow). These can be "heavy" and if the user doesn't care about them, they shouldn't have to bring them in.

Describe the solution you'd like

These dependencies (except for rewrite-java of course) should be optional. Thus, a dependency on rewrite-static-analysis should not automatically pull them in. Instead the client application should provide them and rewrite-static-analysis should mark them as "provided" (Maven parlance), which I believe would translate to the compileOnly Gradle configuration.

Additionally, the recipes need to make sure to not fail with runtime exceptions, if these dependencies are "missing". Thus, utility visitors like CSharpFileChecker should be based on reflection. (Possibly it would make sense to have a generic visitor in rewrite-core, which can be instantiated with a class name, but this is optional and maybe not even a good idea.)

Have you considered any alternatives or workarounds?

Additional context

Are you interested in contributing this feature to OpenRewrite?