Allow closing scene tab preview using Escape

[tbreese3]

Fixes #90706

This PR is a potential implementation for closing the tooltip window which appears after hovering over a tab in the editor.

To test this code, open multiple scenes in the editor, hover over an inactive scene and once the panel pops up, press escape to close it.

[RedMser]

Instead of a new keybind, you can check for ui_cancel since that's what tooltips also do.

[tbreese3]

I modified it to check for ui_cancel. That being said, I feel like it should go in EditorSceneTabs::_scene_tab_input, but when I put it in there, I get very inconsistent behavior because events aren't sent there after adding a new tab for some reason. If it should be in there, I could spend some time debugging and trying to figure out why a call isn't always sent to EditorSceneTabs::_scene_tab_input, just let me know.

[tbreese3]

I made some changes based on your comments. Sorry if my solution is kind of naive, this is my first time working with open source. Also, let me know if there is anything else that should be done differently. Thank you for the feedback.

[tbreese3]

It should be squashed down to one commit now. Is there anything else I should do or need to change? (also sorry, I just saw you said after it's approved, I can squash it again after if I need to make another commit)

[KoBeWi]

Left some more style comments, but the implementation looks alright now.

[tbreese3]

Okay, sounds good, thanks for taking the time to look at this and giving me feedback. I'm super new to this codebase so it was very helpful.

[KoBeWi]

You need to squash again.

[akien-mga]

Thanks! And congrats for your first merged Godot contribution 🎉