activitymanager: Fix header item and missing porting bits

Fix the mistaken port of the local component `Heading` to Kirigami
(yeah, the naming here was quite confusing) and bring back the
filter capability.

While at it finish porting some small bits.
- Port from KQuickControlAddons.KCMShell to KCMUtils.KLauncher
- Fix remaining s/KAuthorize/KAuthorized/ usage.

Amends d4593b3d