### 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(snapshot.transform.key_value("BucketName"))
        with pytest.raises(ClientError) as e:
            aws_client.s3.delete_s(
                Bucket=f"non-existent-bucket-{long_uid()}",
                Delete={"s": [{"Key": "dummy1"}, {"Key": "dummy2"}]},
            )
        assert "NoSuchBucket" == e.value.response["Error"]["Code"]
        snapshot.match("error-non-existent-bucket", e.value.response)
    @markers.aws.validated
    def test_delete_s_encoding(self, s3_bucket, snapshot, aws_client):
        snapshot.add_transformer(snapshot.transform.key_value("Name"))
        _key_1 = "a%2Fb"
        _key_2 = "a/%F0%9F%98%80"
        aws_client.s3.put_(Bucket=s3_bucket, Key=_key_1, Body="percent encoding")
        aws_client.s3.put_(Bucket=s3_bucket, Key=_key_2, Body="percent encoded emoji")
        list_s = aws_client.s3.list_s_v2(Bucket=s3_bucket)
        snapshot.match("list-s-before-delete", list_s)
        response = aws_client.s3.delete_s(
            Bucket=s3_bucket,