Duplicate backpack sprites with local lists/variables can only show one monitor

[kchadha]

Expected Behavior

When adding a sprite from the backpack you should be able to toggle showing/hiding its monitors.

Monitor showing state should also be preserved.

Actual Behavior

When adding the same sprite with a local variable from your backpack to a project twice, only one monitor can display.

Steps to Reproduce

1. Open a new project while logged into scratch.
2. Create a new local list (available to this sprite only)
3. Add things to the list
4. Add the sprite with the list to your backpack
5. Drag the sprite back from your backpack into the same project (or into 2 times into a new project)
6. Try toggling the monitors for the list, only one will show

Found this issue while investigating #7919

[kchadha]

Note that adding just one instance of the sprite from the backpack and then duplicating it via the sprite context menu option works correctly.