Move kernel baseline tests to front_end.

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

Index: pkg/kernel/testcases/spec-mode/arithmetic.baseline.txt
diff --git a/pkg/kernel/testcases/spec-mode/arithmetic.baseline.txt b/pkg/kernel/testcases/spec-mode/arithmetic.baseline.txt
deleted file mode 100644
index 7c867f369e79e83ffabee0ede28b15c3ea74bed9..0000000000000000000000000000000000000000
--- a/pkg/kernel/testcases/spec-mode/arithmetic.baseline.txt
+++ /dev/null
@@ -1,18 +0,0 @@
-library;
-import self as self;
-import "dart:core" as core;
-
-static method foo(core::int x, core::int y) → core::int {
-  dynamic z = x.+(y);
-  return z.<<(4);
-}
-static method loop(core::List<dynamic> xs) → void {
-  core::int _ = xs.length;
-  for (core::int i = 0; i.<(xs.length); i = i.+(1)) {
-  }
-}
-static method main() → dynamic {
-  self::foo(4, 5);
-  self::foo(6, 7);
-  self::loop(<dynamic>["dfg"]);
-}