### 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(
        self,
        fn_name: str,
        path: str,
    ) -> None:
        test_result = self._test_api_gateway_lambda_proxy_integration_no_asserts(fn_name, path)
        data, resource, result, url, path_with_replace = test_result
        self.assertEqual(result.status_code, 203)
        self.assertEqual(result.headers.get("foo"), "bar123")
        self.assertIn("set-cookie", result.headers)
        try:
            parsed_body = json.loads(to_str(result.content))
        except json.decoder.JSONDecodeError as e:
            raise Exception(
                "Couldn't json-decode content: {}".format(to_str(result.content))
            ) from e
        self.assertEqual(parsed_body.get("return_status_code"), 203)
        self.assertDictEqual(parsed_body.get("return_headers"), {"foo": "bar123"})
        self.assertDictEqual(
            parsed_body.get("queryStringParameters"),
            {"foo": "foo", "bar": ["bar", "baz"]},
        )
        request_context = parsed_body.get("requestContext")
        source_ip = request_context["identity"].pop("sourceIp")
        self.assertTrue(re.match(r"^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$", source_ip))
        expected_path = "/" + self.TEST_STAGE_NAME + "/lambda/foo1"
        self.assertEqual(expected_path, request_context["path"])
        self.assertIsNone(request_context.get("stageVariables"))
        self.assertEqual(TEST_AWS_ACCOUNT_ID, request_context["accountId"])
        self.assertEqual(resource.get("id"), request_context["resourceId"])