Allows SpinBox to drop focus when pressing Escape

[KoBeWi]

Describe the project you are working on

Various GUI apps.

Describe the problem or limitation you are having in your project

I'm annoyed by SpinBoxes not being able to easily lose focus. I often run into a situation where I input some number and then try to do something, but can't because SpinBox eats my input. It's especially a problem when there is no other control that you can click to release the focus. Also it doesn't help that the only way to remove focus is using left click, which can sometimes lead to unwanted actions, like painting something in an editor.

Describe the feature / enhancement and how it helps to overcome the problem or limitation

SpinBox should lose focus when pressing Escape.

Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams

Here's the implementation:
godotengine/godot@e6aaab0
The change actually had to be done in LineEdit, because it's what SpinBox uses internally.

If this enhancement will not be used often, can it be worked around with a few lines of script?

It can, but if you need to attach such script to every SpinBox then it probably qualifies as used often.

Is there a reason why this should be core and not an add-on in the asset library?

See above. There is no global solution that can be an addon.