### 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_
SIGNATURE_V2_PARAMS,
    SIGNATURE_V4_PARAMS,
    SYSTEM_METADATA_SETTABLE_HEADERS,
)
from localstack.services.s3.exceptions import InvalidRequest, MalformedXML
from localstack.utils.aws import arns
from localstack.utils.aws.arns import parse_arn
from localstack.utils.strings import (
    checksum_crc32,
    checksum_crc32c,
    hash_sha1,
    hash_sha256,
    to_bytes,
    to_str,
)
from localstack.utils.urls import localstack_host
LOG = logging.getLogger(__name__)
checksum_keys = ["ChecksumSHA1", "ChecksumSHA256", "ChecksumCRC32", "ChecksumCRC32C"]
BUCKET_NAME_REGEX = (
    r"(?=^.{3,63}$)(?!^(\d+\.)+\d+$)"
    + r"(^(([a-z0-9]|[a-z0-9][a-z0-9\-]*[a-z0-9])\.)*([a-z0-9]|[a-z0-9][a-z0-9\-]*[a-z0-9])$)"
)
TAG_REGEX = re.compile(r"^[\w\s.:/=+\-@]*$")
S3_VIRTUAL_HOSTNAME_REGEX = (
    r"(?P<bucket>.*).s3.(?P<region>(?:us-gov|us|ap|ca|cn|eu|sa)-[a-z]+-\d)?.*"
)
_s3_virtual_host_regex = re.compile(S3_VIRTUAL_HOSTNAME_REGEX)
RFC1123 = "%a, %d %b %Y %H:%M:%S GMT"
_gmt_zone_info = ZoneInfo("GMT")
def get_owner_for_account_id(account_id: str):