MDL-38700 course: add tests for moveto_module()

* Test visibility when moving around hidden sections
* Test for visiblity changes when moving around in the same sections.
MDL-38700 course: only change visibility if a module moves to a different section
MDL-38703 course: backport visibility tests from MDL-36417
MDL-38703 course: moving a hidden course module unhides it

When moving to a non-hidden section because visibleold was not
being correctly set. visibleold should only be differnet from visible
when a CM is changed by section visibility
MDL-38713 course: correctly set visibleold on mod creation

Remove uncessary set of visibleold in the form
Updated LAE_readme for 2.3.6+LAE3.0.7 release.