[src/kcms/*] Replace foreach (deprecated) with range/index-based for

Summary:
Add KF6 TODO about removing KURIFilterModule::load(), it's been redundant
for a long time (circa 2014).

Test Plan: make && ctest

Reviewers: Frameworks, dfaure, meven, davidedmundson

Reviewed By: davidedmundson

Subscribers: kde-frameworks-devel

Tags: Frameworks

Differential Revision: https://phabricator.kde.org/D27894