frontend: Use generic timeout in integration test

Created by: fkling

I'm extracting Percy / general integration test stuff from #36044 into a separate (this) PR.

While working on integration tests for the search query input and trying to figure out how to handle waiting on the editor if we want to be able to test different editor implementations (Monaco/CodeMirror), I noticed that the timeout for waiting on the editor gives other components time to "settle". This became evident after I removed one of the editor checks.

But that means that irrespectively of whether or not an editor is rendered on the page, there are pages with components which need time to settle. Using a generic timeout (instead of waiting for something that doesn't exist anyway) expresses that intent better. And that generic timeout also will leave enough time for the editor(s) to update.

I also flipped the order in which we take screenshots so that we don't have to switch back the color scheme (and wait for that) again (the assumption seems to be that light mode is default).

Test plan

CI tests should pass.

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