Improve market actor efficiency handling terminated sectors

[anorth]

The market actor method on_miner_sectors_terminate inefficiently loads the collection root for both proposals and deal states for each deal in the terminated sector/s. Refactor the state type to load the collection once and then perform operations on the collection, before then saving the collection root.

[jbarnes850]

Hey @anorth and @rjan90, are you comfortable if I jump in and start working on this?

[jennijuju]

Hey @anorth and @rjan90, are you comfortable if I jump in and start working on this?

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