### 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
integrations,
                env=env,
                region_name=region_name,
            )
    
    client.create_deployment(restApiId=api_id, stageName=stage_name)
    return api
def create_api_gateway_integrations(
    api_id, resource_id, method, integrations=None, env=None, region_name=None
):
    if integrations is None:
        integrations = []
    client = connect_to_service("apigateway", env=env, region_name=region_name)
    for integration in integrations:
        req_templates = integration.get("requestTemplates") or {}
        res_templates = integration.get("responseTemplates") or {}
        success_code = integration.get("successCode") or "200"
        client_error_code = integration.get("clientErrorCode") or "400"
        server_error_code = integration.get("serverErrorCode") or "500"
        request_parameters = integration.get("requestParameters") or {}
        
        client.put_integration(
            restApiId=api_id,
            resourceId=resource_id,
            httpMethod=method["httpMethod"],
            integrationHttpMethod=method.get("integrationHttpMethod") or method["httpMethod"],
            type=integration["type"],
            uri=integration["uri"],
            requestTemplates=req_templates,
            requestParameters=request_parameters,