Visibility fixes for partners that are also applicants

[wes-otf]

Fixes #3892. This solution was a bit unruly (especially ugly after linting) but it seemed like the logical approach without refactoring the whole visibility_for to be a normal method rather than a class method. This fix evaluates if the partner/reviewer is the author of the source submission first before evaluating the their role. The reviewer role was also lumped in here because even though I know we advise against a reviewer also being an applicant, it still could happen without oversight.

I tried to keep the code as clean as I could and reuse QuerySets, but let me know if y'all see any way I can optimize!

Test Steps

• [ ] Follow the same test steps as #3744, but ensure the partner user also has the role of Applicant
  • Only steps regarding the partner account's visibility need to be followed

[wes-otf]

@frjo if you get the time can you give this a test? I'd like to get this patch in soon

[frjo]

Works well in my testing.