class SyntaxTree::YARV::GetInstanceVariable

### Summary

‘getinstancevariable` pushes the value of an instance variable onto the stack. It uses an inline cache to avoid having to look up the instance variable in the class hierarchy every time.

This instruction has two forms, but both have the same structure. Before Ruby 3.2, the inline cache corresponded to both the get and set instructions and could be shared. Since Ruby 3.2, it uses object shapes instead so the caches are unique per instruction.

### Usage

~~~ruby @instance_variable ~~~