In "Create New Node", retain node focus when clearing search text

[bernhardbarker]

When inserting a new node, I often want to see related nodes. For example, I might want to:

• See all nodes inheriting from PhysicsBody2D.
  • Although currently, typing "physicsbody" returns no results. This makes sense without this feature since you can't insert it and you can't do anything else with the UI. It would also make sense to change that if this is implemented.
• See nodes that might be similar to CharacterBody2D.
• Select a particular node, when I've forgotten the name of that node.

These may not really be use cases for those extensively familiar with all the node types. But it's more relevant for developers who are newer to Godot or those using nodes they haven't used that often.

I propose that when the user clears the search text, it should retain focus on whichever node was selected.

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After typing some search text:

And then erasing the text, don't reset the list of nodes:

Instead, keep focus on whichever one was selected:

Having it reset makes search a lot less useful.