This is a very simple fix to a rather complicated issue. Essentially,
hold-taps will "release" (raise) their captured keys before actually
telling the event manager they have captured a key. This means the event
manager ends up assigning the `last_listener_index` to the hold-tap
subscription rather than the combo. So when the combo calls
`ZMK_EVENT_RELEASE` it raises after the hold-tap instead of after the
combo as the combo code expects.
The corresponding test (which fails without this change) has also been added.
0086ff99c5