Expose account storage root in API

[thaarok]

StateDB (and so even Carmen facade) should provide GetStorageRoot(address) method to obtain the storage root of an account.

There are two use cases:

• checking if the storage of the account is empty during a contract deployment (only compared with EmptyRootHash)
  • Necessary for the go-ethereum upgrade, required by EIP-7610: core/vm: reject contract creation if the storage is non-empty ethereum/go-ethereum#28912
• part of the witness proof - returned as part of eth_getProof output
  • (this may be already part of the witness proof integration?)

[HerbertJordan]

Based on the requirements, I would argue that a HasEmptyStorage(Address) function would be sufficient.

The use of the storage hash in the proof is implicit anyway, no need to expose it in the facade.

[HerbertJordan]

Alternative name: IsStorageEmpty(Address)

[cabrador]

This is not necessary for now since the need for implementing HasEmptyStorage has been proven as not needed anymore.
Investigation done by @HerbertJordan summarized in this comment revealed that this code would not actually be used.

Solution for sonic would be to always return an empty hash.