feature: Replace `legacy` wait strategy with health check expressions
# Feature Request
## Why
What is the use case for the feature you are requesting? What are you trying to solve?
In https://repo1.dso.mil/big-bang/bigbang/-/merge_requests/7755 we switched the [`waitStrategy`](https://fluxcd.io/flux/components/helm/helmreleases/#wait-strategy) to `legacy` to prevent BB from rolling back if any package fails. We should implement a more robust strategy.
## Proposed Solution
If possible, provide details on the proposed solution.
We should implement [health check expressions](https://fluxcd.io/flux/components/helm/helmreleases/#health-check-expressions) instead. We might (or might not) want BB to rollback if "core" packages don't fully reconcile, but probably not for any add-on or other packages. We may want to check beyond "created the helm release" though. In any case, we should switch back to the `poller` `waitStrategy`.
issue