Add export command palette

[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.

Add a secondary command palette, parallel to the query pallete, that lets you run imperative commands to export your response data.

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?

This runs arbitrary shell commands, so users are fully capable of shooting their own feet here.

There may be demand to export request bodies as well, in which case we'll have to generalize this some more.

QA

How did you test this?

Unit test, manual testing

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