### 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
region_name = region_name or get_region()
    pattern = re.sub(r"\([^\|]+\|.+\)", type, pattern)
    result = pattern.replace(".*", "%s") % (region_name, account_id, entity_name)
    if version:
        result = "%s:%s" % (result, version)
    return result
def lambda_function_name(name_or_arn):
    if ":" in name_or_arn:
        arn = parse_arn(name_or_arn)
        if arn["service"] != "lambda":
            raise ValueError("arn is not a lambda arn %s" % name_or_arn)
        return parse_arn(name_or_arn)["resource"].split(":")[1]
    else:
        return name_or_arn
def state_machine_arn(name, account_id=None, region_name=None):
    pattern = "arn:aws:states:%s:%s:stateMachine:%s"
    return _resource_arn(name, pattern, account_id=account_id, region_name=region_name)
def stepfunctions_activity_arn(name, account_id=None, region_name=None):
    pattern = "arn:aws:states:%s:%s:activity:%s"
    return _resource_arn(name, pattern, account_id=account_id, region_name=region_name)
def fix_arn(arn):
    """Function that attempts to "canonicalize" the given ARN. This includes converting
    resource names to ARNs, replacing incorrect regions, account IDs, etc."""
    if arn.startswith("arn:aws:lambda"):
        parts = arn.split(":")
        region = parts[3] if parts[3] in get_valid_regions() else get_region()
        return lambda_function_arn(lambda_function_name(arn), region_name=region)
    LOG.warning("Unable to fix/canonicalize ARN: %s", arn)
    return arn
def cognito_user_pool_arn(user_pool_id, account_id=None, region_name=None):