Add Playwright test for activating a mod with a built-in integration config

[mnholtz]

Create a Playwright test that effectively replaces the manual regression checklist test "Activate a mod that automatically uses the built-in integration configuration" under the "Extension Console Activation" test group: https://www.notion.so/pixiebrix/Release-Checklist-Template-6d435dbf9a464f119ac6202b05d9c3b5?pvs=4#3afe7c8fc2f84c70a6ab86a8b5c1bcc0

Acceptance Criteria

Add a Playwright test that:

• Activates a mod via the Extension console that uses an integration with a built-in integration config, e.g. @pixies/giphy/giphy-search
• Make sure to assert that the integration field on the activation page is pre-populated with the built-in integration (the user should not have to configure anything to activate the mod)
• Verify that the mod works in https://pbx.vercel.app/
• May involve mocking the integration
• After merging, remove the test from the regression checklist notion template https://www.notion.so/pixiebrix/Release-Checklist-Template-6d435dbf9a464f119ac6202b05d9c3b5?pvs=4#3afe7c8fc2f84c70a6ab86a8b5c1bcc0