Return new cursor position from `reshape_info()`

[dgkf]

Currently, after issue only a "change" action from the LSP, the entire region of replaced text is selected after the code action. Instead, it would be more intuitive if the same cursor remained selected through the transformation, mapping its original position to its final position.

To support this, it would be helpful if reshape_info also returned the new cursor position. The rest can be handled on the languageserver side.