### 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_
snapshot.add_transformer(RegexTransformer(region_2, "<region_2>"))
        bucket_name = f"bucket-{short_uid()}"
        client = aws_client_factory(region_name=region_1).s3
        s3_create_bucket_with_client(
            client,
            Bucket=bucket_name,
        )
        target_bucket = s3_create_bucket(CreateBucketConfiguration={"LocationConstraint": region_2})
        with pytest.raises(ClientError) as e:
            bucket_logging_status = {
                "LoggingEnabled": {
                    "TargetBucket": target_bucket,
                    "TargetPrefix": "log",
                },
            }
            client.put_bucket_logging(Bucket=bucket_name, BucketLoggingStatus=bucket_logging_status)
        snapshot.match("put-bucket-logging-different-regions", e.value.response)
        nonexistent_target_bucket = f"target-bucket-{long_uid()}"
        with pytest.raises(ClientError) as e:
            bucket_logging_status = {
                "LoggingEnabled": {
                    "TargetBucket": nonexistent_target_bucket,
                    "TargetPrefix": "log",
                },
            }
            client.put_bucket_logging(Bucket=bucket_name, BucketLoggingStatus=bucket_logging_status)
        snapshot.match("put-bucket-logging-non-existent-bucket", e.value.response)
        assert e.value.response["Error"]["TargetBucket"] == nonexistent_target_bucket
    @markers.aws.validated
    def test_put_bucket_logging_cross_locations(