Adding multiple instances of a few features for 2025 near term needs

[shell1]

Co-enrollment is coming for desktop later this year - but there are some cases that we want covered ASAP. There are also possibly some features where co-enrollment isn't the ideal answer (or is more than is needed).

While we discuss when to co-enroll versus not... can we agree on a few short term feature needs? See this doc where Shell's started gathering ideas. https://docs.google.com/document/d/1W0UL4kiVRgWhCsmQ5tmdgBEgeuMYB7KMCHc-IU7DFII/edit?tab=t.0

1. Emergency Pref Flips Desktop Caution 1-5 (Nimbus team) - long term this is better fixed with co-enrollment. But until that lands and is well tested - if we have 2 emergencies at the same time release management is blocked without having multiple features.
2. Longterm Holdback Desktop Caution # 1-5 (Nimbus team) - This is an issue first thing in January - as we want to start holdbacks in 2025 with New Tab and Growth both. Maybe we just make "Longterm Holdback Desktop Caution New Tab" and "Longterm Holdback Desktop Caution Growth"... and only make another if someone asks?
3. No-feature-testing Desktop Caution 1-5 (Nimbus team) - Growth team is already using the no-feature for the holdbacks on Android and iOS (as they had to launch early to catch the first January app build/release). Thinking we start using the "no-feature testing desktop caution #) on for 2025 so Nimbus can use our testing feature again. Thinking this is also a good feature for any reach testing teams might need to do.

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