Improve 2D editor's right-click menu

[KoBeWi]

• adds "Paste Node(s) Here" option (originally requested here)
  • available only if there is at least 1 CanvasItem in node clipboard
• adds "Move Node(s) Here" option (I vaguely remember someone mentioning it; the dialog is small anyways, so adding more actions won't hurt)
  • available only if there is at least 1 CanvasItem currently selected
• renames "Instance Scene Here" to "Instantiate Scene Here"
  

Putting as draft for now, because global positions don't work correctly.

btw apparently we don't have Paste and Move icons (unless they are named differently), so the new options have no icon. Suggestions for icons appreciated.

[Mickeon]

Could ActionPaste.svg be used for "Paste Node(s) Here"?

Also, perhaps the icon of the Move Tool could be used for "Move Node(s) Here", since... it does what it does.

[fire-forge]

Could "Paste/Move Node(s) Here" be changed to use "Node" and "Nodes" depending on whether multiple nodes are selected instead of just putting "(s)" on the end? This would probably also require adding two different translations so it could be done for other languages as well.

[KoBeWi]

Ok added the new icons:

Could "Paste/Move Node(s) Here" be changed to use "Node" and "Nodes" depending on whether multiple nodes are selected instead of just putting "(s)" on the end?

It could, but we don't do that anywhere in the editor, so actually no.

[KoBeWi]

I managed to fix the global positions, but I got too derailed into improving paste behavior, so I decided to move it into a separate PR: #56906
It needs to be merged before this one (right now this won't compile)

[KoBeWi]

Rebased and simplified the code. I also fixed node positions being not precise.

[akien-mga]

Thanks!