Introduce a new method KotlinClassFinder#findBuiltInsData, which is only
implemented correctly in the JvmCliVirtualFileFinder because it's only used in
the compiler code at the moment.
Introduce JvmBuiltInsPackageFragmentProvider, the purpose of which is to look
for .kotlin_builtins files in the classpath and provide definitions of
built-ins from those files.
Also exclude script.runtime from compilation because, as other excluded
modules, it has no dependency on the stdlib and is no longer compilable from
the IDE now, because it cannot resolve built-ins from anywhere
Alexander Udalov