Add the drop-down to navigate between activities

1. Enable the multilang filter plugin for both content and headings.
2. Do the setup steps outlined in MDL-59612. But this time, ensure that you create activity names in multilang. e.g.

   Assignment 1 <span class="multilang" lang="ja">JA</span><span class="multilang" lang="en">EN</span><span class="multilang" lang="de">DE</span>

3. You can optionally install additional language packs (e.g. ja and de).

As an admin that can see hidden and stealth activities.

1. Login as an admin/teacher
2. Go to an activity that is available.
   • Confirm that you can see a dropdown menu in between the previous and next activity links.
   • Confirm that the pre-selected option in the dropdown menu says "Jump to..."
3. Expand the dropdown menu.
   • Confirm that the stealth activities are not listed.
   • Confirm that hidden activities are listed, but have "(hidden)" beside their activity names.
   • Confirm that the activities with multilang names are displayed appropriately based on the current language.
   • Confirm that the current activity that you're on is not listed in the dropdown menu.

As a student.

1. Go to an activity that is available.
   • Confirm that you can see a dropdown menu in between the previous and next activity links.
   • Confirm that the pre-selected option in the dropdown menu says "Jump to..."
2. Expand the dropdown menu.
   • Confirm that as a student, only the activities available to you are listed on the dropdown menu.
   • Confirm that the activities with multilang names are displayed appropriately based on the current language.
   • Confirm that the current activity that you're on is not listed in the dropdown menu.

Course with a single activity

1. Login as an admin
2. Create a course that only contains a single activity (e.g. assignment)
3. Go to the assignment.
   • Confirm that the activity list dropdown is not being rendered.