Investigate better field access performance by refining bytecode shapes

JEP 416 replaces the old implementation using Unsafe operation for field access with MethodHandle (VarHandle does not have customization which shows performance difference in microbenchmark).

Vladimir Ivanov suggests an idea to refine bytecode shapes for field access to enable concrete MethodHandle or VarHandle be reliably optimized by JIT irrespective of whether receiver is constant or not.