Timeline's Grade button should take teacher to the assignment grading page with All submissions to be graded (resetting any active course group filter)

(This issue is related to https://tracker.moodle.org/browse/MDL-73945 , which urges that teachers of multiple course groups should always access the total overview of their to-do work in the Timeline - unaffected by any previously set course group filters.)

Steps to reproduce:

1. Teacher teaches 2 or more groups in a course, has added an Assignment (group mode: Separate or Visible groups), added "Remind me to grade by" date in the settings.
2. Students from several groups have submitted work - thus assignments from various groups are due to be graded.
3. While working in the course, teacher at some point switched the course group filter from "All participants" to, say, "Group A".
4. After some time, having forgotten about the activated group filter, the teacher visits the Timeline, sees the "Grade" button and the number of assignments to grade (incorrectly counting only Group A submissions - cf. MDL-73945)
5. Teacher clicks on the "Grade" button, is taken to the assignment grading page.
6. The grading page does NOT display any information about the active group filter - teacher can directly grade only Group A submissions here, and can be unaware that submissions from other groups are yet to be graded.

Expected behaviour / solution:

1) In line with the MDL-73945 proposal, I advise that the Teacher's “Grade” button in the Timeline should link to the assignment grading page, always resetting the group filter to “All participants”. This way the teacher will never miss any due grading that needs to be done in the course.

2) I also strongly propose that the assignment's group mode info (Separate groups or Visible groups) and the group filter switch be displayed on the Grade assignment page, allowing the Teacher to switch the group filter as desired (as on the “View submissions” page.)