Add basic Functional test for text format settings form

Added a basic Functional test class CollapseTextFormatSettingsFormTest which opens the Filtered HTML text format settings form and enables the Collapse Text filter by submitting the form.

This test was mostly added for 🐛 Fix missing schema Active to ensure the problem introduced in versions above 10.3, could be fixed by the changes suggested in the ticket.

For the tests to pass until the related issue is fixed, the Gitlab CI file of the module had to be modified to force testing by default for versions lower than 10.3, so currently 10.2.x-dev.

Thanks in advance for your feedback!

Automatically closed - issue fixed for 2 weeks with no activity.