### 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/
apigw_client = aws_stack.connect_to_service("apigateway")
        s3_client = aws_stack.connect_to_service("s3")
        bucket_name = "test-bucket"
        object_name = "test.json"
        object_content = '{ "success": "true" }'
        object_content_type = "application/json"
        api = apigw_client.create_rest_api(name="test")
        api_id = api["id"]
        s3_client.create_bucket(Bucket=bucket_name)
        s3_client.put_object(
            Bucket=bucket_name,
            Key=object_name,
            Body=object_content,
            ContentType=object_content_type,
        )
        self.connect_api_gateway_to_s3(bucket_name, object_name, api_id, "GET")
        apigw_client.create_deployment(restApiId=api_id, stageName="test")
        url = gateway_request_url(api_id, "test", "/")
        result = requests.get(url)
        self.assertEqual(200, result.status_code)
        self.assertEqual(object_content, result.text)
        self.assertEqual(object_content_type, result.headers["content-type"])
        
        apigw_client.delete_rest_api(restApiId=api_id)
        s3_client.delete_object(Bucket=bucket_name, Key=object_name)
        s3_client.delete_bucket(Bucket=bucket_name)
    def test_api_mock_integration_response_params(self):