Remove bytecodes aconst_init, withfield and <vnew> method from Valhalla

[hangshao0]

The new bytecodes aconst_init and withfield previously introduced in Project Valhalla is going to be removed. Value Type initialization will be done via existing bytecodes new, dup and putfield.

The special Value Type constructor <vnew> is also going to be removed. It will be replaced with regulated constructor (mentioned in #18309).

[hzongaro]

Previously if a new bytecode was executed for a value type, an InstantiationError would result. As with the anticipated removal of the Q prefix, I think the JIT compiler will require a helper so it can determine at compile-time whether it's working in an environment where new can be applied to a value type. That way, the compiler can support both ways of creating value type instances while we wait for the transition.

[hangshao0]

OpenJDK/Javac support for these changes are not completed yet. It is not an urgent issue, so OpenJ9 could make these changes once things are ready.