## 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.
## Why this should be merged
`goheader` linter apparently hasn't been running but now decided to and
is blocking another PR. It's not worth the time to investigatie why
(probably a version update).
## How this works
Update header comments as required.
## How this was tested
N/A
## Why this should be merged
To allow more thorough handling of duplicate state roots (or any other
info other users would like), additional information can be provided to
a call of `statedb.Commit`. This change allows arbitrary types to be
sent to `triedb` as well as the `SnapshotTree`. However, this is a
breaking change for those using the functionality already, since the
snapshot commit option is wrapped with another call.
## How this works
See the edited libevm test for usage.
## How this was tested
Edited test case to include `TrieDBUpdateOption` and ensures the payload
is sent.
## Why this should be merged
Allows for a drop-in replacement of `snapshot.Tree` (i.e. one that uses
block hashes instead of state roots). This is intended as a temporary
solution while we investigate having the state root affected by the
block hash to remove path ambiguity.
## How this works
Introduction of:
1. `state.SnapshotTree` interface to match methods required on
`snapshot.Tree` as used by `state.StateDB`; and
2. `stateconf` package for variadic options plumbed by
`StateDB.Commit()` through to `SnapshotTree.Update()`.
Although variadic (to maintain function call-signature compatibility)
only the `stateconf.WithUpdatePayload(any)` is expected to be used.
Recipients of the options can access the payload with
`stateconf.ExtractUpdatePayload()`.
## How this was tested
Unit test demonstrating propagation of `stateconf.UpdateOption` payload.
