[autotests] Rewrite testShellClientRules

Summary:
Currently, the test doesn't verify that each rule does what it should,
e.g. a force rule is a force rule and not force temporarily, etc. This
as it turns out hides some bugs, e.g. all remember rules do not work,
forced window shortcuts can't be released, etc.

CCBUG: 403305

Reviewers: #kwin, davidedmundson

Reviewed By: #kwin, davidedmundson

Subscribers: davidedmundson, graesslin, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D18464