### 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 copy
import json
import logging
import random
import re
import threading
import time
import traceback
from typing import Dict, List
from requests.models import Request, Response
from localstack import config, constants
from localstack.services.awslambda import lambda_api
from localstack.services.dynamodb.utils import (
    ItemFinder,
    ItemSet,
    SchemaExtractor,
    calculate_crc32,
    extract_table_name_from_partiql_update,
)
from localstack.services.dynamodbstreams import dynamodbstreams_api
from localstack.services.generic_proxy import ProxyListener, RegionBackend
from localstack.utils.analytics import event_publisher
from localstack.utils.aws import aws_responses, aws_stack