## Why this should be merged
`ava-labs/coreth` has a partitioned state-address space, achieved by
setting or clearing a specific bit in the hash used to key the space.
This change allows such behaviour to be achieved with pure `libevm`
instead of the `StateDB` wrapping that `coreth` currently uses.
## How this works
Introduction of `state.StateDBHooks` interface, including a
`TransformStateKey()` method that allows for arbitrary change of state
key. If registered, this hook will be honoured by
`StateDB.{Get,GetCommitted,State}Key()` methods unless they receive a
`stateconf.SkipStateKeyTransformation` option.
## How this was tested
Unit test of `SetState() -> GetState() + GetCommittedState()` round trip
with and without options to skip.
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