## Description 

Setting the stage for higher speed replays and replaying batch from FN
local state.
Added support for replaying checkpoints concurrently.
Added support for replaying whole epochs.
Simplified code.

## Test Plan 

Manual testing

---
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### Type of Change (Check all that apply)

- [ ] user-visible impact
- [ ] breaking change for a client SDKs
- [ ] breaking change for FNs (FN binary must upgrade)
- [ ] breaking change for validators or node operators (must upgrade
binaries)
- [ ] breaking change for on-chain data layout
- [ ] necessitate either a data wipe or data migration

### Release notes