feat: don't show masters-only columns for courses without a masters track

[jansenk]

Only show masters-only columns when a course has a master's track.

No Masters track / mode:

Masters track / mode

Note: This is based on TRACKS. As shown in the screenshot above, you can technically have a student who is enrolled as "masters" without a masters track in a course BUT this is only possible through manual developer modification and can't happen in normal user-facing environments.

FYI: @openedx/content-aurora

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 100.00%. Comparing base (6778948) to head (32be24c). Report is 51 commits behind head on master.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #324 +/- ## ========================================= Coverage 100.00% 100.00% ========================================= Files 122 122 Lines 1274 1281 +7 Branches 250 253 +3 ========================================= + Hits 1274 1281 +7 ```

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[farhaanbukhsh]

@mphilbrick211 This will require a proposal.

@jansenk Are you willing to pursue these changes?