### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When attempting to sign some document using Localstack KMS inside a lambda container (also running on localstack), the localstack KMS listener returns some unknown error.

The KMS key and lambda containers have been created from the same CDK app deploy, and I can see all the resources in the localstack web console.

The test application I'm using to prove this behaviour is available here:
https://github.com/LukaHedt/localstack_kms_test

Instructions to run are in the main Readme, and the `/localstack/Readme.md` file.

`aws-sdk` returns an unknown error, and the localstack docker logs that I receive are available here:
https://pastebin.com/58Z3fXi3

Have done an amount of testing and can confidently claim the following:
- Have tested on multiple machines with the same outcome
- Doesn’t make a difference if I specify an ARN or a KeyID in the signing request
- Downgrading localstack versions either didn’t make a difference, or I couldn’t actually deploy a localstack container with version 0.12.20 or lower.

### Expected Behavior

KMS Sign should return a signature for the given payload.

### How are you starting LocalStack?

With a docker-compose file

### Steps To Reproduce

Test application demonstrating the current behaviour is available here:

https://github.com/LukaHedt/localstack_kms_test

Full instructions to run are in the `/localstack/Readme.md` file.


### Environment

```markdown
- OS: MacOS Monteray 12.3
- LocalStack: 0.14.0
```


### Anything else?

_No response_
import base64
import json
import logging
import time
from typing import Dict, List
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives import serialization as crypto_serialization
from cryptography.hazmat.primitives.asymmetric import ec, padding, rsa
from moto.kms.exceptions import ValidationException
from moto.kms.models import Key, kms_backends
from localstack.services.generic_proxy import ProxyListener, RegionBackend
from localstack.services.kms.kms_starter import KMS_PROVIDER
from localstack.utils.analytics import event_publisher
from localstack.utils.aws import aws_stack
from localstack.utils.aws.aws_responses import set_response_content
from localstack.utils.common import json_safe, long_uid, select_attributes, to_bytes, to_str
LOG = logging.getLogger(__name__)
EVENT_KMS_CREATE_KEY = "kms.ck"
VALID_OPERATIONS = [
    "Decrypt",
    "Encrypt",
    "GenerateDataKey",