* add an update_cache flag to get_state to have more granular control over when we write to the cache
* State cache tweaks
- add state-cache-headroom flag to control pruning
- prune old epoch boundary states ahead of mid-epoch states
- never prune head block's state
- avoid caching ancestor states unless they are on an epoch boundary
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Co-authored-by: Michael Sproul <michael@sigmaprime.io>
## Issue Addressed
#3708
## Proposed Changes
- Add `is_finalized_block` method to `BeaconChain` in `beacon_node/beacon_chain/src/beacon_chain.rs`.
- Add `is_finalized_state` method to `BeaconChain` in `beacon_node/beacon_chain/src/beacon_chain.rs`.
- Add `fork_and_execution_optimistic_and_finalized` in `beacon_node/http_api/src/state_id.rs`.
- Add `ExecutionOptimisticFinalizedForkVersionedResponse` type in `consensus/types/src/fork_versioned_response.rs`.
- Add `execution_optimistic_finalized_fork_versioned_response`function in `beacon_node/http_api/src/version.rs`.
- Add `ExecutionOptimisticFinalizedResponse` type in `common/eth2/src/types.rs`.
- Add `add_execution_optimistic_finalized` method in `common/eth2/src/types.rs`.
- Update API response methods to include finalized.
- Remove `execution_optimistic_fork_versioned_response`
Co-authored-by: Michael Sproul <michael@sigmaprime.io>
