Add support for chained / next actions

Summary:
This adds support for multiple actions following each
other through the "Next" value of Action dictionaries.

Test Plan: Activates the corresponding part of the visibilitytest.

Reviewers: #okular

Subscribers: sander, aacid

Tags: #okular

Maniphest Tasks: T8278

Differential Revision: https://phabricator.kde.org/D11609