Use a single struct type to store all MVs
There are currently two main structs used to store MVs: IntMv and Mv. However, the (x,y) components of the MV are stored in different orders in the two structs, making them confusing to use together, and presenting a potential source of bugs. Instead, a single, universal type should be decided on, and should be used to store all MVs in the code, to avoid confusion and reduce the likelihood of bugs.