Replace JSONPath queries with commands

[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 is the first of a new set of features geared around using command line tools within the app for transforming and navigation response bodies. The JSONPath query box has been replaced with a mini shell, where you can execute arbitrary commands using the response body as stdin. For example, you can use jq .args to filter down to the args field.

The reason for this is to expand the capabilities of the filtering, without having to add first-class support for everything within Slumber. There will be further improvements to this to make it easier to use and more powerful.

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 is a breaking change, so it will be part of 3.0. This may decrease usability because it requires users to have separate tools installed, but the tradeoff is worth it IMO. We could potentially provide certain tools out of the box anyway to improve it.

QA

How did you test this?

updated existing tests, wrote one new one

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