Complete interpreter instructions at the end

[clarus]

The goal of this issue is to complete the definition of the interpreter for the following instructions:

• PackGeneric
• Unpack
• UnpackGeneric
• ReadRef
• WriteRef
• CastU8
• CastU16
• CastU32
• CastU64
• CastU128
• CastU256
• Add
• Sub
• Mul
• Mod
• Div
• BitOr
• BitAnd
• Xor

The interpreter is defined in the file https://github.com/formal-land/coq-of-rust/blob/main/CoqOfRust/move_sui/simulations/move_vm_runtime/interpreter.v