Enhancement: Split button row generation into a new UI widget class

[pushfoo]

Enhancement request:

What should be added/changed?

Generating a row of buttons from labels should become a dedicated UI element. An unencapsulated version of this behavior is currently present in UIMessageBox:

arcade/arcade/gui/constructs.py

Lines 59 to 63 in 1187225

	button_group = UIBoxLayout(vertical=False, space_between=10)
	for button_text in buttons:
	button = UIFlatButton(text=button_text)
	button_group.add(button)
	button.on_click = self.on_ok # type: ignore

What would it help with?

It would make it easier to create button rows for other UI elements such as the file chooser (#1201). For example, the bottom row of buttons in this mockup could be implemented using the proposed widget:

[JackAshwell11]

I've submitted #1253 which adds a UIButtonRow class.

[eruvanos]

Fixed with #1580

Will be released within 3.0.