Move submit buttons in often used forms to sticky footer

As Moodle has a huge variety of features, the forms to add / edit course or activity settings or to use backup / restore functions tend to be really large, also if some sub-sections are collapsed. This implies a lot of scrolling down to the submit buttons also if you (as a teacher) just want to do the necessary settings (usually at the top of the form, e.g. title and content).

To make especially course editing more smooth, I'd suggest to move the submit buttons of moodle forms to a sticky footer as it has been done in mod_data for Moodle 4.1. I've started a discussion some time ago at https://moodle.org/mod/forum/discuss.php?d=438672 .

The code used there is obsolete in my opinion as tusefomal has already provided a much better solution in MDL-75134.