test: update e2es to use the new insightsUserConfiguration controller for setting high-contrast mode

[dbjorge]

Description of changes

This updates all the existing E2E tests to use the new insightsUserConfiguration controller in the background page to set high-contrast mode for accessibility tests, rather than using the details page UI to do it. This:

• Cuts 2-3min off e2e runtime
• Removes a bunch of operations that would otherwise be opportunities for flakiness
• Cooperates better with upcoming permissions changes that would otherwise prevent the use of the details view UI without popping the popup UI first

Mechanically, this allows for a bunch of simplification of the existing tests, since they no longer need to spawn separate browser instances/pages in a lot of cases; there was a pattern of having 2 top level describe blocks for "normal mode" vs "high contrast" mode that I've eliminated and replaced with updating a11y tests to just do it.each over the 2 HC states.

As part of this, I updated the guidance content tests to work more similar to every other test case, where we do a11y scans in both HC/non-HC modes but only snapshot the components in one of the 2 modes. This is where most of the "30k lines deleted" comes from.

Pull request checklist

• [n/a] Addresses an existing issue: #0000
• Ran yarn fastpass
• [n/a] Added/updated relevant unit test(s) (and ran yarn test)
• [n/a] Verified code coverage for the changes made. Check coverage report at: <rootDir>/test-results/unit/coverage
• PR title AND final merge commit title both start with a semantic tag (fix:, chore:, feat(feature-name):, refactor:). Check workflow guide at: <rootDir>/docs/workflow.md
• [n/a] (UI changes only) Added screenshots/GIFs to description above
• [n/a] (UI changes only) Verified usability with NVDA/JAWS

[smoralesd]

This is a great improvement to our e2e!!! Kudos.

[smoralesd]

A couple of minor/not-high-priority comments, LGTM otherwise