### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

Currently the VTL template for `request_templates` is not processed properly:

```
#set( $body = $input.json("$") )

#macro( loop $map )
{
    #foreach($key in $map.keySet())
        #set( $k = $util.escapeJavaScript($key) )
        #set( $v = $util.escapeJavaScript($map.get($key)).replaceAll("\\'", "'") )
        "$k": "$v"
        #if( $foreach.hasNext ) , #end
    #end
}
#end

{
    "enhancedAuthContext": #loop($context.authorizer),

    "headers": #loop($input.params().header),

    "query": #loop($input.params().querystring),

    "path": #loop($input.params().path),

    "identity": #loop($context.identity),

    "stageVariables": #loop($stageVariables),
}
EOF
}
```

results in,

```
'

{
    "enhancedAuthContext": {
    }
,

    "headers": {
    }
,

    "query": {
    }
,

    "path": {
    }
,

    "identity": {
    }
,

    "stageVariables": {
    }
,
}
'
```

### Expected Behavior

The template should be rendered and have the JSON properties.

### How are you starting LocalStack?

Custom (please describe below)

### 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)

    awslocal s3 mb s3://mybucket


### Environment

```markdown
- OS: MacOS
- LocalStack: 0.14
```


### Anything else?

This example can be used to validate.
https://github.com/localstack/localstack-terraform-samples/tree/master/apigateway-lambda-velocity
global LOCAL_REGION
    if LOCAL_REGION is None:
        session = boto3.session.Session()
        LOCAL_REGION = session.region_name or ""
    return config.DEFAULT_REGION or LOCAL_REGION
def is_internal_call_context(headers):
    """Return whether we are executing in the context of an internal API call, i.e.,
    the case where one API uses a boto3 client to call another API internally."""
    auth_header = headers.get("Authorization") or ""
    return get_internal_credential() in auth_header
def get_internal_credential():
    return "Credential=%s/" % INTERNAL_AWS_ACCESS_KEY_ID
def set_internal_auth(headers):
    authorization = headers.get("Authorization") or ""
    if authorization.startswith("AWS "):
        
        authorization = re.sub(
            r"AWS [^/]+",
            "AWS %s" % get_internal_credential(),
            authorization,
        )
    else:
        authorization = re.sub(
            r"Credential=[^/]+/",
            get_internal_credential(),
            authorization,
        )
    headers["Authorization"] = authorization
    return headers
def get_local_service_url(service_name_or_port: Union[str, int]) -> str: