Fix input bindings involving shift and a character

[LucasPickering]

Description

Describe the change. If there is an associated issue, please include the issue link (e.g. "Closes #xxx"). For UI changes, please also include screenshots.

When a key combination involves "shift", crossterm reports the keycode as a capital letter (e.g. KeyCode::Char('G')). This was breaking the equality matching.

Closes #401

Known Risks

What issues could potentially go wrong with this change? Is it a breaking change? What have you done to mitigate any potential risks?

Further fragile logic. Mitigated with some tests. I totally believe there's other input bugs in there though.

QA

How did you test this?

Added some unit tests, tested in the TUI

Checklist

• Have you read CONTRIBUTING.md already?
• Did you update CHANGELOG.md?
  • Only user-facing changes belong in the changelog. Internal changes such as refactors should only be included if they'll impact users, e.g. via performance improvement.
• Did you remove all TODOs?
  • If there are unresolved issues, please open a follow-on issue and link to it in a comment so future work can be tracked