Define an detail::OperandStorage class to handle managing instruction...

Define an detail::OperandStorage class to handle managing instruction operands. This class stores operands in a similar way to SmallVector except for two key differences. The first is the inline storage, which is a trailing objects array. The second is that being able to dynamically resize the operand list is optional. This means that we can enable the cases where operations need to change the number of operands after construction without losing the spatial locality benefits of the common case (operation instructions / non-control flow instructions with a lifetime fixed number of operands).

PiperOrigin-RevId: 231910497