Move kernel baseline tests to front_end.

pkg/front_end/testcases/rasta/switch_fall_through.dart.dartk.expect

 library;
 import self as self;
 import "dart:core" as core;
 
 static method main() → dynamic {
   #L1:
   switch(1) {
     #L2:
     case 1:
       {
@@ skipping 36 matching lines @@
         }
         finally {
         }
         throw core::_fallThroughError();
       }
     #L7:
     case 10000:
       "Should be last. No fall-through error, falling through allowed here.";
   }
 }