dot/state: fix `Rewind` by adding lookup for finalized block -> (round, setID) where block was finalized

[noot]

Task summary

• Rewind is currently broken as it fails to set what the current grandpa round and setID are after rewinding
• requires some lookup for finalized block -> (round, setID) where block was finalized
• implement and fix this

[timwu20]

@kishansagathiya are you working on this?

[kishansagathiya]

@timwu20 no, un-assigning