refactor(combo): Use key-bindings controller

[rkaraivanov]

This commit migrates the combo component to use the general key-bindings controller from the library. Aside from unifying the implementation across components this also improves several behaviors of the combo:

• Keyboard events inside the combo are no longer "swallowed".
• Tab navigation is more natural, i.e. there are no longer 2 tab stops per combo component.

Updated the combo test suite to accommodate for the changes.