Suggest possible imports when reporting a “symbol not found” error

[julienrf]

Currently, if you try to apply a method defined as an extension method, but without importing it, the compiler reports and error and suggests you the possible imports that would make the extension method available.

However, the compiler does not suggest you the possible imports you could add to fix “symbol not found” errors (e.g., if you write Monad.apply without first importing cats.Monad).

I believe that would be a useful addition. Many IDEs already do that, but I guess it would be even better if the compiler handled it, and the IDEs could reuse that information directly.