MethodHandles: Remove experimental flag.

Runtime::IsMethodHandlesEnabled now always returns true.
This change also removes the (now unnecessary) run scripts
for method handle tests.

Note that the --experimental=method-handles flag is left in
place for the test build steps (etc/default-build) because it's still a
convenient way to supply arguments to jack / smali.

Test: make test-art-host

Change-Id: I8475c7b8ac2615ac382a06ce54be39dce3cc7713
diff --git a/runtime/runtime.h b/runtime/runtime.h
index 8fc211c..a87e1c1 100644
--- a/runtime/runtime.h
+++ b/runtime/runtime.h
@@ -304,7 +304,7 @@
   }
 
   bool IsMethodHandlesEnabled() const {
-    return experimental_flags_ & ExperimentalFlags::kMethodHandles;
+    return true;
   }
 
   void DisallowNewSystemWeaks() REQUIRES_SHARED(Locks::mutator_lock_);