Run the Baloo runner out of process

Summary:
KRunner now supports querying data from running processes rather than
being plugins.

Due the number of crash reports of Baloo in both krunner and more
importantly plasmashell, we can move this out of process to make the UX
better in the event of an issue.

This also means we share the database instance between both krunner and plasmashell.

Test Plan:
Searched, typing really quickly
All works as before; including forcing a delay when you only type a few letters
Results are just as fast as before to the human eye (bustle show calls as 0ms)

Tested open with folder and open normally actions
Tested dragging from krunner to dolphin
Tested we had correct icons

Reviewers: #plasma, broulik

Reviewed By: #plasma, broulik

Subscribers: broulik, plasma-devel

Tags: #plasma

Differential Revision: https://phabricator.kde.org/D7404