Fix evaluation order with object spread (#11412)

* Fix object spread runtime semantics

* limit this deoptimization

* optimize empty objects

* declare variables

packages/babel-plugin-proposal-object-rest-spread/test/fixtures/object-spread/side-effect/exec.js

@@ -0,0 +1,4 @@
+var k = { a: 1, b: 2 };
+var o = { a: 3, ...k, b: k.a++ };
+
+expect(o).toEqual({a: 1, b: 1});