Each of this tasks should be solved in an independent PR

1. Refactor GetReverseStateDiff function in `blockchain.go to return by value. Spread the change to every piece of code that interacts with this function.
2. Refactor AdaptOrderedMessageToL1 (in vm2core.go) to receive by reference and return by value

Then in sn2core.go:

1. RefactorAdaptBlock to return by value.
2. Refactor AdaptTransactionReceipt to return by value
3. The same for adaptGasConsumed
4. The same for AdaptEvent
5. AdaptExecutionResources
6. AdaptL1ToL2Message
7. AdaptL2ToL1Message
8. AdaptStateUpdate
9. AdaptStateDiff
10. Refactor AdaptCompiledClass by renaming it AdaptCasmClass and return by value (core.Casm instead of *core.Casm)
11. Refactor AdaptSierraClass to return by value