### 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_
alias_name = f"alias/{short_uid()}"
        assert _get_alias(kms_client, alias_name) is None
        kms_create_alias(AliasName=alias_name)
        assert _get_alias(kms_client, alias_name) is not None
        kms_client.delete_alias(AliasName=alias_name)
        assert _get_alias(kms_client, alias_name) is None
    @pytest.mark.aws_validated
    def test_update_alias(self, kms_client, kms_create_key, kms_create_alias):
        alias_name = f"alias/{short_uid()}"
        old_key_id = kms_create_key()["KeyId"]
        kms_create_alias(AliasName=alias_name, TargetKeyId=old_key_id)
        alias = _get_alias(kms_client, alias_name, old_key_id)
        assert alias is not None
        assert alias["TargetKeyId"] == old_key_id
        new_key_id = kms_create_key()["KeyId"]
        kms_client.update_alias(AliasName=alias_name, TargetKeyId=new_key_id)
        alias = _get_alias(kms_client, alias_name, new_key_id)
        assert alias is not None
        assert alias["TargetKeyId"] == new_key_id
    
    
    @pytest.mark.only_localstack
    def test_get_put_list_key_policies(self, kms_client, kms_create_key):
        base_policy = {
            "Version": "2012-10-17",
            "Id": "key-default-1",
            "Statement": [
                {
                    "Sid": "This is the default key policy",