Replace FlipFlip usage with Feature class

[JPrevost]

• Removes FlipFlop Gem
• Updates code and tests to use Feature class instead of FlipFlip
• Stabilizes test suite

Side effects:

• Moved some geo tests to their own file to match other similar tests
• Updated some tests that had a condition in them that should never occur
• GeoData stage and prod have had FEATURE_GEODATA=true added to config. We can remove GDT=true after this is deployed

Developer

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• ANDI or WAVE has been run in accordance to our guide.
• This PR contains no changes to the view layer.
• New issues flagged by ANDI or WAVE have been resolved.
• New issues flagged by ANDI or WAVE have been ticketed (link in the Pull Request details above).
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New ENV

• All new ENV is documented in README.
• All new ENV has been added to Heroku Pipeline, Staging and Prod.
• ENV has not changed.

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Additional context needed to review

E.g., if the PR includes updated dependencies and/or data
migration, or how to confirm the feature is working.

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Code

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  added technical debt.

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  (not just this pull request message).
• The documentation has been updated or is unnecessary.
• New dependencies are appropriate or there were no changes.

Testing

• There are appropriate tests covering any new functionality.
• No additional test coverage is required.

[jazairi]

I don't think I've ever been happier to approve a PR. :) Thanks for figuring this out and dealing with the slog of replacing FlipFlop in all of the tests!

I did have one question about the GeoData feature name in the README. If it actually is FEATURE_GDT, then I think this is ready to merge. If not, then fixing that is the only issue I see here.