AwsProxyHttpServletRequest.getParameterMap() not support multiple query string

* Framework version: 1.2
* Implementations: Spring

## Scenario
My http request is `<scheme>://<host>/<path>?id=xxx&id=yyy`

Function in controller is `func(@RequestParam MultiValueMap<String, String> params)`

## Expected behavior

Value of `params`  is 
```
{
  "id": ["xxx", "yyy"]
}
```

## Actual behavior

Value of `params`  is 
```
{
  "id": ["xxx"]
}
