Stop using XRay in Firefox

[muodov]

Reviewer:

Description:

https://app.asana.com/0/1201614831475344/1207277833550158/f
Firefox now supports execution worlds for content scripts in their MV2 manifest. This allows us to remove xray code. See also

Steps to test this PR:

Automated tests:

• Unit tests
• Integration tests

Reviewer Checklist:

• Ensure the PR solves the problem
• Review every line of code
• Ensure the PR does no harm by testing the changes thoroughly
• Get help if you're uncomfortable with any of the above!
• Determine if there are any quick wins that improve the implementation

PR Author Checklist:

• Get advice or leverage existing code
• Agree on technical approach with reviewer (if the changes are nuanced)
• Ensure that there is a testing strategy (and documented non-automated tests)
• Ensure there is a documented monitoring strategy (if necessary)
• Consider systems implications

[muodov]

@sammacbeth the test failures seem unrelated, the amp ones seem to be broken in main too, and others do pass locally. I assume it's not related to the change?