Extract Difficulty Tabs Into Own Component

[otobot1]

Is your feature request related to a problem? Please describe.
The difficulty tabs are rendered by the main ModsTable component. The ModsTable component is already very cluttered.

Describe the solution you'd like
Extract the difficulty tabs into their own component (in a new file). This will make the ModsTable component at least slightly more clean.

Describe alternatives you've considered
N/A

Additional context
Follow-up to #752 issue 1.

This change may be tricky/impossible. When a fix was attempted as part of an earlier PR, the difficulty tabs started breaking when the page was hot-reloaded by Next.js dev mode. If this can be fixed/worked-around, great. If not, it's a huge deal to leave things the way they are.