### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

We are using the `Authorization` header for routing purposes

```
 "authorization: AWS4-HMAC-SHA256 <...>"
```

https://github.com/localstack/localstack/issues/5770

### Expected Behavior

Use a custom header to avoid causing confusion with backend integrations

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

Run a custom HTTP integration without authorisation

### Environment

```markdown
- OS: 
- LocalStack:
```


### Anything else?

No
if not port:
        port = config.EDGE_PORT
    if config.EDGE_PORT_HTTP and config.EDGE_PORT_HTTP != port:
        do_start_edge(
            config.EDGE_BIND_HOST,
            config.EDGE_PORT_HTTP,
            use_ssl=False,
            asynchronous=True,
        )
    if port > 1024 or is_root():
        return do_start_edge(config.EDGE_BIND_HOST, port, use_ssl, asynchronous=asynchronous)
    
    class Terminator(object):
        def stop(self, quiet=True):
            try:
                url = "http%s://%s:%s" % ("s" if use_ssl else "", LOCALHOST, port)
                requests.verify_ssl = False
                requests.post(url, headers={HEADER_KILL_SIGNAL: "kill"})
            except Exception:
                pass
    
    TMP_THREADS.append(Terminator())
    return run_process_as_sudo("edge", port, asynchronous=asynchronous)
def run_process_as_sudo(component, port, asynchronous=False, env_vars=None):