Similar to CONTRIB-8573.

When the default presentation is set by default, if the checkbox "Pre-uploading presentation enabled" is unchecked, the URL for the presentation file is never sent to BBB.

The option should only enable or disable the UI for Teachers to customize (or not) the default presentation.

The correct behaviour should be:

A) if checkbox is ticked in plugin settings show preuploaded presentation feature to Teachers in Activity settings.

A.a) if checkbox is ticked in plugin settings, and the activity does have a presentation file attached, use the activity presentation
A.b) if checkbox is ticked in plugin settings, and the activity does NOT have a presentation file attached, use the default presentation defined in the settings. Which means, if default presentation is defined, use it, if it is not, let BBB use its default one.

B) if checkbox is NOT ticked in plugin settings DO NOT show preuploaded presentation feature to Teachers in Activity settings.

B.a) if checkbox is NOT ticked in plugin settings, and the activity does have a presentation file attached (due a previous setting), still ignore the activity presentation and try to use the default one defined in settings
B.a) if checkbox is NOT ticked in plugin settings, and the activity does NOT have a presentation file attached (due a previous setting), try to use the default one defined in settings

The wording should also be changed from "Pre-uploading presentation enabled" to "Pre-uploading presentation can be edited"