Summary:
Export actionForId as a method in menuImporter

IDs are used in the low level API which the appmenu kded module wants to
use directly.

Fix arguments in itemActivationRequest

We have a int actionId and a uint window timestamp in porting somehow
these had got swapped and renamed. This now matches the relevant DBus
signal they connect to.

Open correct acton sub-menu on loading

So pressing alt+e will open the edit menu immediately when showing the
application menu.

Also remove existing leftover code that did this which is using a member
var which was previously never set.

Test Plan:
Had the relevant emit patch in plasma-integration
Pressed alt+e, got the edit menu

Reviewers: #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D4832