Fix (Whiteboards): Shape index and arrow binding issue

[sprocketc]

• Fixed persisting and undoing shape index changes. To reproduce the issue, place shapes on top of each other and click [ or ] to change their order. After changing their original order, navigate to a different page or undo the action. You will see that the index changes are not persisted, and cannot be undone. Reintroduced the index property of shapes to fix persist. If the current index is different from the shape index, we update its nonce. Also added update-shapes-index to update the order on undo/redo. I removed bump from page, since it doesn't do anything anymore.
• Fixed an issue with arrow bindings and undo/redo, To reproduce this, create two shapes, connect them with an arrow, delete one of them, undo the delete action and move the previously deleted shape. The arrow should follow the shape.
• Fixed a minor overflow issue on references modal (see https://discord.com/channels/725182569297215569/1056543757065003048/1088117614070480928)

[tiensonqin]

Work as described! 🚢

[tiensonqin]

❤️

[tiensonqin]

In the future, I hope we can use fractional Indexing for the shapes index and store it in the blocks instead of the page's properties, the current implementation needs to transact all the indexes when adjusting the position of one shape. Another benefit is that it makes real-time collaboration development easier.