Move kernel baseline tests to front_end.

pkg/kernel/testcases/spec-mode/call.baseline.txt

-library;
-import self as self;
-import "dart:core" as core;
-
-class Callable extends core::Object {
-  constructor •() → void
-    : super core::Object::•()
-    ;
-  method call(dynamic x) → dynamic {
-    return "string";
-  }
-}
-class CallableGetter extends core::Object {
-  constructor •() → void
-    : super core::Object::•()
-    ;
-  get call() → dynamic
-    return new self::Callable::•();
-}
-static method main() → dynamic {
-  dynamic closure = (dynamic x) → dynamic => x;
-  dynamic int1 = closure.call(1);
-  dynamic int2 = closure.call(1);
-  dynamic int3 = closure.call.call(1);
-  dynamic int4 = closure.call.call.call(1);
-  dynamic callable = new self::Callable::•();
-  dynamic string1 = callable.call(1);
-  dynamic string2 = callable.call(1);
-  dynamic string3 = callable.call.call(1);
-  dynamic string4 = callable.call.call.call(1);
-  dynamic callableGetter = new self::CallableGetter::•();
-  dynamic string5 = callableGetter.call(1);
-  dynamic string6 = callableGetter.call(1);
-  dynamic string7 = callableGetter.call.call(1);
-  dynamic string8 = callableGetter.call.call.call(1);
-  dynamic nothing1 = closure.call();
-  dynamic nothing2 = closure.call();
-  dynamic nothing3 = closure.call.call();
-  dynamic nothing4 = closure.call.call.call();
-  dynamic nothing5 = callable.call();
-  dynamic nothing6 = callable.call();
-  dynamic nothing7 = callable.call.call();
-  dynamic nothing8 = callable.call.call.call();
-  dynamic nothing9 = callableGetter.call();
-  dynamic nothing10 = callableGetter.call();
-  dynamic nothing11 = callableGetter.call.call();
-  dynamic nothing12 = callableGetter.call.call.call();
-}