### 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
request_context = {
        "resourcePath": resource_path or relative_path,
        "apiId": api_id,
        "domainPrefix": api_id,
        "domainName": domain_name,
        "accountId": account_id,
        "resourceId": resource_id,
        "requestId": long_uid(),
        "identity": {
            "accountId": account_id,
            "sourceIp": source_ip,
            "userAgent": headers.get("User-Agent"),
        },
        "httpMethod": method,
        "protocol": "HTTP/1.1",
        "requestTime": pytz.utc.localize(datetime.datetime.utcnow()).strftime(
            REQUEST_TIME_DATE_FORMAT
        ),
        "requestTimeEpoch": int(time.time() * 1000),
    }
    
    auth_context = invocation_context.auth_context
    if auth_context:
        request_context["authorizer"] = auth_context
    request_context["identity"].update(invocation_context.auth_identity or {})
    if not is_test_invoke_method(method, path):
        request_context["path"] = (f"/{stage}" if stage else "") + relative_path
        request_context["stage"] = stage
    return request_context
def apply_request_response_templates(