Make the `IList` type more accessable

[jon-wurtz]

VSCode type checkers get mad if you hint an output as list instead of IList. With a little checking, you can find IList to be under kirin.dialects.ilist.IList and is not imported by default. Could this be made a little easier to find, e.g. kirin.IList after import kirin?

[Roger-luo]

or we should re-export it in downstream packages? I don't see why user would touch kirin (or even know there is this package exists to build the downstream language)