Refactor view state

[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.

This refactors the exchange pane and it's children to be single-use, meaning we trash the component and build a new one whenever the request state changes. This makes the state management much simpler. I'd like to move toward this pattern more in general.

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?

State bugs. We have decent test coverage to guard against this.

QA

How did you test this?

Bit of manual testing, mostly relying on existing tests

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