fix: focus item on click caused by Enter or Space keys

[web-padawan]

Description

Fixes vaadin/web-components#7142

Based on vaadin/web-components#7111

Note: unlike the WC monorepo version (V22+), in V14 we have native <button> element handling click events, and we aren't calling click() manually on keydown. So I had to update tests to use enter() / space() followed by click().

Type of change

• Bugfix

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