[Tracking upstream] Remove erasStakersClipped from api.derive.staking._erasExposure when applicable

[TarikGul]

Via #5771 api.derive.staking._erasExposure needed to change its internal functionality to accommodate the new changes. Currently the derive has forward and backwards compatibility via #5815.

That being said, once all relay chain runtimes are updated to 1004000 it is safe to say we can remove the erasStakersClipped, and have support for only erasStakersPaged. This means we can also adjust the types to ensure there is a single source of truth for the _eraExposure.

This is a tracking issue to ensure we stay on top of it and will be added to the projects board tracking column.

[ScepticMatt]

how would you get erasStakersClipped from api.at(hash) then? I haven't been able to use derive API with historical data

[TarikGul]

That being said, once all relay chain runtimes are updated to 1004000 it is safe to say we can remove the erasStakersClipped, and have support for only erasStakersPaged

This is referring only to the functionality in the derive, not api.query

[TarikGul]

I changed the title to be more less confusing.