Add subsegment splits to end of run menu

[Panzerhandschuh]

I will follow up with some improvements to the stage checkpoint splits so that they are evenly spaced and the x-axis has the appropriate labels ("4-1", "4-2", etc.)

Linear map:

Staged map:

Checks

• I have thoroughly tested all of the code I have modified/added/removed to ensure something else did not break
• I have followed semantic commit messages e.g. feat: Add foo, chore: Update bar, etc...
• My branch has a clear history of changes that can be easy to follow when being reviewed commit-by-commit
• My branch is functionally complete; the only changes to be done will be those potentially requested in code review
• All changes requested in review have been fixuped into my original commits.
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