### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

When creating base-path-mappings on an API Gateway, there is a special `(none)` path when you don't specify a path during creation. Localstack stores this as `basePath: "(none)"` internally.
When you query to get the base paths, the URLs are escaped by the client (verified in both awscli and terraform) so the basePath is sent as `%28none%29` in the url.
Localstack doesn't appear to be decoding urls and when you attempt to get-base-path-mapping it fails in a string comparison of `(none)` to `%28none%29`.

```shell
> aws --endpoint-url=http://localhost:4566 apigateway get-base-path-mapping --domain-name example.com --base-path "(none)"

An error occurred (NotFoundException) when calling the GetBasePathMapping operation: Base path mapping not found: %28none%29
```

### Expected Behavior

When you attempt to get-base-path-mappings after creating one with the (none) path, it succeeds and returns the mapping.

```
> aws --endpoint-url=http://localhost:4566 apigateway get-base-path-mapping --domain-name example.com --base-path "(none)"

{
    "basePath": "(none)",
    "restApiId": "uyy4c3dsho",
    "stage": "dev"
}
```


### How are you starting LocalStack?

With the `localstack` script

### Steps To Reproduce

#### How are you starting localstack (e.g., `bin/localstack` command, arguments, or `docker-compose.yml`)

    make start

#### Client commands (e.g., AWS SDK code snippet, or sequence of "awslocal" commands)

    awslocal apigateway create-rest-api --name "testgw"
    awslocal apigateway create-base-path-mapping --domain-name example.com --rest-api-id <from output above> --stage dev
    awslocal apigateway get-base-path-mapping --domain-name example.com --base-path "(none)"



### Environment

```markdown
- OS: fedora 34
- LocalStack: latest
```


### Anything else?

https://docs.aws.amazon.com/apigateway/api-reference/link-relation/basepathmapping-by-base-path/
self.assertEqual("AWS", rs["type"])
        self.assertEqual("POST", rs["httpMethod"])
        self.assertEqual(target_uri, rs["uri"])
        # invok
        url = gateway_request_url(api_id=api_id, stage_name=self.TEST_STAGE_NAME, path="/test")
        response = requests.get("%s?param1=foobar" % url)
        self.assertLess(response.status_code, 400)
        content = json.loads(to_str(response.content))
        self.assertEqual("GET", content.get("httpMethod"))
        self.assertEqual(api_resource["id"], content.get("requestContext", {}).get("resourceId"))
        self.assertEqual(self.TEST_STAGE_NAME, content.get("requestContext", {}).get("stage"))
        self.assertEqual('{"param1": "foobar"}', content.get("body"))
        # delet
        rs = apigw_client.delete_integration(
            restApiId=api_id,
            resourceId=api_resource["id"],
            httpMethod="GET",
        )
        self.assertEqual(200, rs["ResponseMetadata"]["HTTPStatusCode"])
        with self.assertRaises(ClientError) as ctx:
            # This 
            apigw_client.get_integration(
                restApiId=api_id, resourceId=api_resource["id"], httpMethod="GET"
            )
        self.assertEqual(ctx.exception.response["Error"]["Code"], "NotFoundException")
        
        lambda_client = aws_stack.connect_to_service("lambda")
        lambda_client.delete_function(FunctionName=lambda_name)
        apigw_client.delete_rest_api(restApiId=api_id)
    def test_api_gateway_handle_domain_name(self):