### 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
"""Fix the account ID in the ARNs returned in the given Flask response or string"""
    existing = existing or ["123456789", "1234567890", "123456789012", MOTO_ACCOUNT_ID]
    existing = existing if isinstance(existing, list) else [existing]
    replace = replace or TEST_AWS_ACCOUNT_ID
    is_str_obj = is_string_or_bytes(response)
    content = to_str(response if is_str_obj else response._content)
    replace = r"arn{col}aws{col}\1{col}\2{col}{acc}{col}".format(col=colon_delimiter, acc=replace)
    for acc_id in existing:
        regex = r"arn{col}aws{col}([^:%]+){col}([^:%]*){col}{acc}{col}".format(
            col=colon_delimiter, acc=acc_id
        )
        content = re.sub(regex, replace, content)
    if not is_str_obj:
        response._content = content
        response.headers["Content-Length"] = len(response._content)
        return response
    return content
def inject_test_credentials_into_env(env):
    if ENV_ACCESS_KEY not in env and ENV_SECRET_KEY not in env:
        env[ENV_ACCESS_KEY] = "test"
        env[ENV_SECRET_KEY] = "test"
def inject_region_into_env(env, region):