Make possible to scale multiple nodes at once in the canvas editor

[YeldhamDev]

This PR makes possible to change the scale of multiple selected canvas items at once:

Screencast_20241025_163951.webm

And adds some smaller improvements:

• Make the "scale" gizmo be positioned at the temporary pivot when used.
• Show the "move" gizmo when multiple items are selected (no idea why this wasn't done sooner).

Sponsored By: 🐺 Lone Wolf Technology / 🍀 W4 Games.

[KoBeWi]

When in Select mode, pressing Ctrl+Alt will show scale gizmo, but pressing Alt does not show move gizmo.

godot.windows.editor.dev.x86_64_bgD7PZffpG.mp4

[fire]

In 3D mode, the local mode and non local mode affects scaling of multiple objects in standard but weird ways.

Reference note for if someone was trying to match behaviour.

#68804

[YeldhamDev]

@KoBeWi

When in Select mode, pressing Ctrl+Alt will show scale gizmo, but pressing Alt does not show move gizmo.

This seems to be unrelated to my PR, as pressing Alt on stable/master doesn't show it either. I can try to fix this too if that's what you meant with your message.

[KoBeWi]

I mean, you added move gizmo when move tool is active. Also the scale gizmo showing is also coming from this PR. So it's related.

EDIT:
Ok I checked again and the scale showing was already there, just for one node. So the move improvement can be done later.

[KoBeWi]

Another thing, which is partially pre-existing bug, is that pressing Ctrl+Alt in move mode will display scale gizmo and with temp pivot you can see 2 gizmos at once.

[KoBeWi]

Aside from that little double gizmo bug, looks good.

[YeldhamDev]

@KoBeWi Only the "Scale" shortcut actually works outside of the "Selection" mode. I wonder if this was an oversight and the behavior should be removed.

[KoBeWi]

Yep, I'd remove it.

[YeldhamDev]

@KoBeWi @AThousandShips Changes made.

[Repiteo]

Thanks!