### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

- Localstack fails with HTTP 500, error code "InternalError", message "not enough values to unpack (expected 2, got 1)" when `CopySource` is an invalid string for `copy_object` API.

### Expected Behavior

- For the same API `copy_object`, the cloud fails with HTTP 400, error code "InvalidArgument".
- Localstack should handle invalid `CopySource` i.e., it is a dictionary with one value or an invalid string not adhering to "{bucket}/{key}" format.

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    docker run localstack/localstack

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    botoclient.copy_object(CopySource="Invalid_random_string", Bucket="test_bucket", Key=key) 


 test_bucket is a valid bucket.  

### Environment

```markdown
- OS: Ubuntu 22.04.2 LTS
- LocalStack: 2.1.0
- boto3: 1.28.6
```


### Anything else?

_No response_
role_name = f"replication_role_{short_uid()}"
        policy_name = f"replication_policy_{short_uid()}"
        role_arn = create_iam_role_with_policy(
            RoleName=role_name,
            PolicyName=policy_name,
            RoleDefinition=S3_ASSUME_ROLE_POLICY,
            PolicyDefinition=S3_POLICY,
        )
        s3_create_bucket(Bucket=bucket_src)
        s3_create_bucket(
            Bucket=bucket_dst, CreateBucketConfiguration={"LocationConstraint": "us-west-2"}
        )
        aws_client.s3.put_bucket_versioning(
            Bucket=bucket_dst, VersioningConfiguration={"Status": "Enabled"}
        )
        # expe
        with pytest.raises(ClientError) as e:
            aws_client.s3.get_bucket_replication(Bucket=bucket_src)
        snapshot.match("expected_error_no_replication_set", e.value.response)
        replication_config = {
            "Role": role_arn,
            "Rules": [
                {
                    "Status": "Enabled",
                    "Priority": 1,
                    "DeleteMarkerReplication": {"Status": "Disabled"},
                    "Filter": {"Prefix": "Tax"},
                    "Destination": {"Bucket": f"arn:aws:s3:::{bucket_dst}"},
                }
            ],