Move ui test to primitives/ui

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

primitives/api/test/tests/ui/positive_cases/empty_impl_runtime_apis.rs

@@ -0,0 +1,11 @@
+// Do not use `construct_runtime!`.
+struct Runtime;
+
+// Empty `impl_runtime_apis!` cannot deduce the Runtime name
+// and should not implement the `runtime_metadata()` method.
+sp_api::impl_runtime_apis! {}
+
+// Expect the test to compile because this has the effect of
+// not calling `construct_runtime!` nor `impl_runtime_apis!`
+// for the Runtime.
+fn main() {}