### Is there an existing issue for this?

- [X] I have searched the existing issues

### Feature description

Currently, we always [calculate](https://github.com/localstack/localstack/blob/256b0de1f1a6085d3994e8d1322c763962ded2f0/localstack/services/kms/models.py#L229-L230) SHA256 digests for messages with `RAW` [MessageType](https://docs.aws.amazon.com/kms/latest/APIReference/API_Sign.html#API_Sign_RequestSyntax).

It is not clear if this is compatible with AWS. There are some reports like [this one](https://github.com/localstack/localstack/issues/6815#issuecomment-1309882776) about our implementation of Sign / Verify not working properly. Could be due to these digests.

What has to be done:
1. Should try to figure out how AWS calculates digests, whether the same algorithm is always used, or if digests are based on [SigningAlgorithm](https://docs.aws.amazon.com/kms/latest/APIReference/API_Sign.html#API_Sign_RequestSyntax). For this we can try importing the same key material into both AWS and LocalStack, use the resulting keys to sign the same message and then compare the signatures. If that works. If not - we can try just creating a key in AWS, sign a message with AWS, export the public key and then go through different digest algorithms in LocalStack, trying to verify the signed message with the obtained public key.
2. If the issue is really in our implementation of digests - should fix the digest logic.

### 🧑‍💻 Implementation

_No response_

### Anything else?

_No response_
self, context: RequestContext, request: ReplicateKeyRequest
    ) -> ReplicateKeyResponse:
        replicate_from_store = self._get_store(context)
        key = replicate_from_store.get_key(request.get("KeyId"))
        key_id = key.metadata.get("KeyId")
        if not key.metadata.get("MultiRegion"):
            raise UnsupportedOperationException(
                f"Unable to replicate a non-MultiRegion key {key_id}"
            )
        replica_region = request.get("ReplicaRegion")
        replicate_to_store = kms_stores[context.account_id][replica_region]
        if key_id in replicate_to_store.keys:
            raise AlreadyExistsException(
                f"Unable to replicate key {key_id} to region {replica_region}, as the key "
                f"already exist there"
            )
        replica_key = copy.deepcopy(key)
        replica_key.metadata["Description"] = request.get("Description", "")
        
        
        replica_key.calculate_and_set_arn(context.account_id, replica_region)
        replicate_to_store.keys[key_id] = replica_key
        return ReplicateKeyResponse(ReplicaKeyMetadata=replica_key.metadata)
    @handler("UpdateKeyDescription", expand=False)
    def update_key_description(