[FR] Board move multiple items to a group with shortcut

### Description

We can now select cards in a board with `Shift + click` or holding `Shift` and using down/up arrow keys.

We have a shortcut for moving *ONE* card to previous/next group, I'd like to enable this behavior for when multiple cards are selected, this is the intended behavior:

**Cards selected from multiple groups**
- When moving cards to previous or next using the shortcut, all cards should move to the group of the card that is selected furthest to the left/right.
- This means that if we have groups A, B, and C, and a card is selected in both group A, and B, and the shortcut `,` is used to move items to the left, all selected cards will end up in group A.
- This means that if we have groups A, B, and C, and a card is selected in both group A, and B, and the shortcut `.` is used to move items to the right, all selected cards will end up in group B.

**Cards selected from same group**
- When moving cards to previous/next group, all cards should move from the same group to the previous/next group

### Impact

Empower kanban users

### Additional Context

See `appflowy_flutter\lib\plugins\database\board\presentation\widgets\board_shortcut_container.dart`