Add the ability to create Instructions without the appropriate operand type

[slxdy]

Because this isn't currently possible, cloning instructions or pre-making instructions before assigning their operator is hell.
It's an unnecessary limitation that simply shouldn't exist.

[slxdy]

My current workaround (not really safe):

public static Instruction CreateInstructionRaw(OpCode opCode, object? operand = null)
{
    var instruction = (Instruction)RuntimeHelpers.GetUninitializedObject(typeof(Instruction));
    instruction.OpCode = opCode;
    instruction.Operand = operand;
    return instruction;
}