### 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
return Mock(boto3.client("apigateway", region_name=config.DEFAULT_REGION))
def test_render_template_values():
    util = templating.VelocityUtil()
    encoded = util.urlEncode("x=a+b")
    assert encoded == "x%3Da%2Bb"
    decoded = util.urlDecode("x=a+b")
    assert decoded == "x=a b"
    escape_tests = (
        ("it's", '"it\'s"'),
        ("0010", "10"),
        ("true", "true"),
        ("True", '"True"'),
        ("1.021", "1.021"),
        ("'''", "\"'''\""),
        ('""', '""'),
        ('"""', '"\\"\\"\\""'),
        ('{"foo": 123}', '{"foo": 123}'),
        ('{"foo"": 123}', '"{\\"foo\\"\\": 123}"'),
        (1, "1"),
        (True, "true"),
    )
    for string, expected in escape_tests:
        escaped = util.escapeJavaScript(string)
        assert escaped == expected
        
        json.loads(escaped)
class TestJSONPatch(unittest.TestCase):