feat: Add "Move Up" / "Move Down" menu items to lib unit components (backport)

[bradenmacdonald]

This is a backport of #3111

This is a workaround for #1994 "Cannot drag a component past a really long component on a unit page" (Since "autoscroll" is disabled in our usage of dnd-kit due to conflicts with our custom collision detection algorithm.)

This implements the workaround proposed in #3110.

I also re-organized the menu to put the destructive remove/delete menu options last, below a divider, for better consistency with course authoring.

Private ref: MNG-4985

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Additional details and impacted files

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[ChrisChV]

Looks good 👍

• I tested this: I followed the testing instructions in a Verawood instance
• I read through the code and considered the security, stability and performance implications of the changes.
• I tested that the UI can be used with a keyboard only (tab order, keyboard controls).
• Includes tests for bugfixes and/or features added.