Port VM1 contract code behind link to VM2 and add state behind link in VM2 contract

[miloszm]

Describe what you want implemented
Contract code was put behind link in VM1, this needs to be ported to VM2. Also, it is beneficial to put contract state behind link as well.

Describe "Why" this is needed
When state changes, contract code does not need to be rewritten when re-serialising the state. State behind link allows contracts to share same state, e.g., in a hamt node.

Describe alternatives you've considered
We could keep contract code and state without links, but this is less efficient as every change in state causes code to be rewritten.

Additional context
Not having a link also causes a storage size bloat. That's why it was introduced in VM1.