Port away from Qt's foreach all loops over method-local containers

Summary:
The simple part of foreach porting, as those containers objects are not
shared with anyone, so the removal of the container copying has no risks.

GIT_SILENT

Reviewers: dfaure

Reviewed By: dfaure

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D23664