### 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/
2, len(rs["items"])
        )  # shoul
        resource = [res for res in rs["items"] if res["path"] == "/test"][0]
        self.assertIn("GET", resource["resourceMethods"])
        
        client.delete_rest_api(restApiId=rest_api_id)
        spec_file = load_file(TEST_IMPORT_REST_API_FILE)
        rs = client.import_rest_api(body=spec_file)
        self.assertEqual(200, rs["ResponseMetadata"]["HTTPStatusCode"])
        rest_api_id = rs["id"]
        rs = client.get_resources(restApiId=rest_api_id)
        resources = rs["items"]
        self.assertEqual(3, len(resources))
        paths = [res["path"] for res in resources]
        self.assertIn("/", paths)
        self.assertIn("/pets", paths)
        self.assertIn("/pets/{petId}", paths)
        
        client.delete_rest_api(restApiId=rest_api_id)
    def test_step_function_integrations(self):
        client = aws_stack.connect_to_service("apigateway")
        sfn_client = aws_stack.connect_to_service("stepfunctions")
        lambda_client = aws_stack.connect_to_service("lambda")
        state_machine_name = "test"
        state_machine_def = {
            "Comment": "Hello World example",
            "StartAt": "step1",
            "States": {
                "step1": {"Type": "Task", "Resource": "__tbd__", "End": True},
            },