### 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_
stream: IO[bytes],
    buffer: IO[bytes],
    content_length: int,
) -> IO[bytes]:
    """
    Decode the incoming stream encoded in `aws-chunked` format into the provided buffer
    :param stream: the original stream to read, encoded in the `aws-chunked` format
    :param buffer: the buffer where we set the decoded data
    :param content_length: the total maximum length of the original stream, we stop decoding after that
    :return: the provided buffer
    """
    buffer.seek(0)
    buffer.truncate()
    written = 0
    while written < content_length:
        line = stream.readline()
        chunk_length = int(line.split(b";")[0], 16)
        while chunk_length > 0:
            amount = min(chunk_length, S3_CHUNK_SIZE)
            data = stream.read(amount)
            buffer.write(data)
            real_amount = len(data)
            chunk_length -= real_amount
            written += real_amount
        
        stream.read(2)
    return buffer
def is_presigned_url_request(context: RequestContext) -> bool: