Compositor: UI: remove snapping to nodes.
Snapping nodes to other nodes behaves in a very unpredictable way, which makes most snapping options useless.
The patch removes the following:
- Snapping options `Node X`, `Node Y` and `Node XY`
- Menu `Snap Node Element`
- Menu `Snap Target`
New behavior:
- Activating `Snap` always acts as 'Snap to Grid'
Part of https://projects.blender.org/blender/blender/issues/128612
Pull Request: https://projects.blender.org/blender/blender/pulls/127667