GDScript: Enable exporting nodes to the inspector

[vnen]

Use the addition from #62185 to allow exporting node types as well. Also fixed a small issue with it.

I notice one bug here that I can't revert it. The revert button is always active and clicking it does nothing, even if the path is cleared. I'm not familiar with the inspector code so I'll leave to someone else to figure it out.

Bugsquad edit:

• Fix Clicking on nodes in the scene tree emits errors: Condition "!pointer_mode" is true. Returning: String() #62461
• Implements Ability to export Node types instead of just NodePaths godot-proposals#1048

[KoBeWi]

I noticed one obvious (?) editor-side problem:

There is no way to tell what node type the property expects without looking into the script (unless your scene contains the expected node type).

EDIT:
btw it does fix #62461

EDIT2:
As for the revert problem, the current property is type NODE_PATH, but the default is type NIL. Hence they are different.
Trying to set null to NodePath assigns an empty NodePath. Or at least it should. For whatever reason this doesn't clear the property if something is assigned.

[akien-mga]

There is no way to tell what node type the property expects without looking into the script (unless your scene contains the expected node type).

It should probably include the node type in the title, and likely filter to show only compatible types as selectable? (Others disabled so the scene tree is still recognizable).

[akien-mga]

Thanks!