### What does this PR do?
- Implements .onEnd
Fixes#22061
Once #22144 is merged, this also fixes:
Fixes#9862Fixes#20806
### How did you verify your code works?
Tests
---
TODO in a followup (#22144)
> ~~Make all entrypoints be called in onResolve~~
> ~~Fixes # 9862~~
> ~~Fixes # 20806~~
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