Update messages for filters on CoachExamsPage (and lessons too)

I spotted this while reviewing #9863 and saw some linting changes in the diff for CoachExamsPage where there are comments indicating that we were temporarily commenting out the Active/Inactive filters for exams in #6174 due to not having updated the strings.

With the guidance from @radinamatic in #6174 we need to be sure we have the correct strings defined in the component and that the select dropdown is visible and working as expected.

Note that CoachExamsPage isn’t the only place where this is an issue, there are others as can be seen in https://github.com/learningequality/kolibri/pull/6233/files (the PR that commented the filters out).

[radinamatic]

This will work very well @jtamiace @akolson 💯

Let’s just make sure we put the proper context for translators:

filterLessonStatus: {
        message: 'Status',
        context: 'Label for the selector used to filter and display lessons by status.',
      },

---

filterLessonAll: {
        message: 'All',
        context: 'Refers to LESSON. Default option in the selector used to filter and display lessons by status. ',
      },

---

filterLessonVisible: {
        message: 'Visible',
        context: 'Refers to LESSON. Option in the selector used to filter and display only the lessons visible  to learners. ',
      },

…and so forth 🙂

[akolson]

@jtamiace Thanks for the design insights. This below seems more consistent with other filters in Kolibri and I think is a better option to pursue.

For lessons: Filter label: Status Options: All, Visible, Not visible

For quizzes: Filter label: Status Options: All, Not started, Started, Ended

@radinamatic any concerns regarding i18n?