Node Wrangler: update for Geometry Nodes

Node Wrangler can now be used in the Geometry Nodes editor.
Summary of the changes for Geometry Nodes:
* Pressing ctrl+shift+LMB will now connect the geometry socket of the
  node (if it exists) to the output socket of the modifier. This is
  similar to the functionality already present for shader and
  compositor nodes.
* Nodes can be merged using a Join Geometry (default) or Boolean node.
* `LinkToOutput` and `ReloadImages` have been disabled, because they
  don't make sense for geometry nodes.
* Other operators work like they do for the other node tree types.

In D9748 and in chat it was accepted that this patch can be merged
into the 2.93 release branch, even though we are quite late in the
release process already.

Differential Revision: https://developer.blender.org/D9748