### 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/
def test_api_gateway_lambda_proxy_integration_with_is_base_64_encoded(self):
        
        content = b"hello, please base64 encode me"
        def _mutate_data(data) -> None:
            data["return_is_base_64_encoded"] = True
            data["return_raw_body"] = base64.b64encode(content).decode("utf8")
        test_result = self._test_api_gateway_lambda_proxy_integration_no_asserts(
            self.TEST_LAMBDA_PROXY_BACKEND_WITH_IS_BASE64,
            self.API_PATH_LAMBDA_PROXY_BACKEND_WITH_IS_BASE64,
            data_mutator_fn=_mutate_data,
        )
        
        self.assertEqual(test_result.result.status_code, 203)
        self.assertEqual(test_result.result.content, content)
    def _test_api_gateway_lambda_proxy_integration_no_asserts(
        self,
        fn_name: str,
        path: str,
        data_mutator_fn: Optional[Callable] = None,
    ) -> ApiGatewayLambdaProxyIntegrationTestResult:
        """
        Perform the setup needed to do a POST against a Lambda Proxy Integration;
        then execute the POST.
        :param data_mutator_fn: a Callable[[Dict], None] that lets us mutate the
          data dictionary before sending it off to the lambda.
        """
        self.create_lambda_function(fn_name)
        
        lambda_uri = aws_stack.lambda_function_arn(fn_name)
        invocation_uri = "arn:aws:apigateway:%s:lambda:path/2015-03-31/functions/%s/invocations"