### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

It seems like whenever I open a connection to `localhost:4566` (4566 being exposed from the localstack container), for the next ~1 second any HTTP calls will have delayed responses. If I open 10 connections, the delay will be 10 seconds.

### Expected Behavior

Multiple connections can be opened and don't impact other requests until a certain connection limit.

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

1. run localstack: `docker run --rm -it -p 4566:4566 --name ls localstack/localstack:0.14.0` - I managed to reproduce it with versions as old as 0.12.0
2. run something like this to see how long curls take inside the container: 

```bash
docker exec -it ls /bin/bash

# inside the container:
while true; do time curl localhost:4566; sleep 0.1; done
```

3. open connections with telnet:

```
telnet localhost 4566
```

4. observe extended response times in the curl loop. For me it's ~1s extra per open connection (I'm simulating opening more connections with a JVM application opening sockets as I request).

### Environment

```markdown
- OS: macOS / ubuntu, tried both x86 and arm64 macs, and an arm64 linux
- LocalStack: 0.12.0, 0.13.1, 0.14.0
```


### Anything else?

This surfaces itself as extremely slow responses whenever you have e.g. a JVM application that keeps a cached connection pool. Even 10 connections in a pool are enough to cause consistent delays every couple seconds (which I think is after the connections are closed due to the defaults on my client), under no additional traffic targeting localstack.
if modified_request_to_backend:
            if modified_request_to_backend.url:
                request_url = get_proxy_backend_url(
                    modified_request_to_backend.url, original_url=request_url
                )
            data_to_send = modified_request_to_backend.data
            if modified_request_to_backend.method:
                method_to_send = modified_request_to_backend.method
        
        headers_to_send.pop("Transfer-Encoding", None)
        response = requests.request(
            method_to_send,
            url=request_url,
            data=data_to_send,
            headers=headers_to_send,
            stream=True,
            verify=False,
        )
    
    
    not_consumed = not getattr(response, "_content_consumed", True)
    pass_raw = not_consumed or response.headers.get("content-encoding") in ["gzip"]
    if pass_raw and getattr(response, "raw", None):
        new_content = response.raw.read()
        if new_content:
            response._content = new_content
    
    for listener in listeners_outbound:
        updated_response = listener.return_response(
            method=method_to_send or handler_chain_request.method,