feat!: Change the way tabs are ordered [BD-38] [TNL-9174] [BB-5076] (#29262)

* feat!: Change the way tabs are ordered
The change imposes a new ordering for tabs based on their new priority. When reordering tabs, this ordering will be maintained.

* fix: Apply suggestions from code review

Co-authored-by: Farhaan Bukhsh <farhaan@opencraft.com>

* fix: review feedback

Co-authored-by: Farhaan Bukhsh <farhaan@opencraft.com>

common/lib/xmodule/xmodule/tabs.py

@@ -302,6 +302,7 @@ class StaticTab(CourseTab):
     type = 'static_tab'
     is_default = False  # A static tab is never added to a course by default
     allow_multiple = True
+    priority = 100
 
     def __init__(self, tab_dict=None, name=None, url_slug=None):
         def link_func(course, reverse_func):
@@ -381,14 +382,14 @@ class CourseTabList(List):
         within the course.
         """
 
-        course.tabs.extend([
+        course_tabs = [
             CourseTab.load('course_info'),
             CourseTab.load('courseware')
-        ])
+        ]
 
         # Presence of syllabus tab is indicated by a course attribute
         if hasattr(course, 'syllabus_present') and course.syllabus_present:
-            course.tabs.append(CourseTab.load('syllabus'))
+            course_tabs.append(CourseTab.load('syllabus'))
 
         # If the course has a discussion link specified, use that even if we feature
         # flag discussions off. Disabling that is mostly a server safety feature
@@ -400,12 +401,16 @@ class CourseTabList(List):
         else:
             discussion_tab = CourseTab.load('discussion')
 
-        course.tabs.extend([
+        course_tabs.extend([
             CourseTab.load('textbooks'),
             discussion_tab,
             CourseTab.load('wiki'),
             CourseTab.load('progress'),
         ])
+        # While you should be able to do `tab.priority`, a lot of tests mock tabs to be a dict
+        # which causes them to throw an error on this line
+        course_tabs.sort(key=lambda tab: getattr(tab, 'priority', None) or float('inf'))
+        course.tabs.extend(course_tabs)
 
     @staticmethod
     def get_discussion(course):