### 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/
"quota": {"limit": 10, "period": "DAY", "offset": 0},
            "throttle": {"rateLimit": 2, "burstLimit": 1},
            "apiStages": [{"apiId": api_id, "stage": "staging"}],
            "tags": {"tag_key": "tag_value"},
        }
        client = aws_stack.connect_to_service("apigateway")
        usage_plan_id = client.create_usage_plan(**payload)["id"]
        key_name = "testApiKey"
        key_type = "API_KEY"
        api_key = client.create_api_key(name=key_name)
        payload = {
            "usagePlanId": usage_plan_id,
            "keyId": api_key["id"],
            "keyType": key_type,
        }
        client.create_usage_plan_key(**payload)
        response = requests.put(
            url,
            json.dumps({"id": "id1", "data": "foobar123"}),
        )
        # when 
        self.assertEqual(403, response.status_code)
        response = requests.put(
            url,
            json.dumps({"id": "id1", "data": "foobar123"}),
            headers={"X-API-Key": api_key["value"]},
        )
        # when 
        self.assertEqual(200, response.status_code)
    def test_multiple_api_keys_validate(self):