### 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/
name = "validator123"
        result = client.create_request_validator(restApiId=rest_api_id, name=name)
        self.assertEqual(200, result["ResponseMetadata"]["HTTPStatusCode"])
        validator_id = result["id"]
        # LIST
        result = client.get_request_validators(restApiId=rest_api_id)
        self.assertEqual(200, result["ResponseMetadata"]["HTTPStatusCode"])
        self.assertEqual([{"id": validator_id, "name": name}], result["items"])
        # GET
        result = client.get_request_validator(
            restApiId=rest_api_id, requestValidatorId=validator_id
        )
        self.assertEqual(200, result["ResponseMetadata"]["HTTPStatusCode"])
        self.assertEqual(
            select_attributes(result, ["id", "name"]),
            {"id": validator_id, "name": name},
        )
        # UPDATE
        result = client.update_request_validator(
            restApiId=rest_api_id, requestValidatorId=validator_id, patchOperations=[]
        )
        # DELETE
        client.delete_request_validator(restApiId=rest_api_id, requestValidatorId=validator_id)
        with self.assertRaises(Exception):
            client.get_request_validator(restApiId=rest_api_id, requestValidatorId=validator_id)
        with self.assertRaises(Exception):
            client.delete_request_validator(restApiId=rest_api_id, requestValidatorId=validator_id)
        
        client.delete_rest_api(restApiId=rest_api_id)
    def test_base_path_mapping(self):