### 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/
matched = re.match(PATH_REGEX_CLIENT_CERTS, path)
    return matched.group(1) if matched else None
def get_client_certificate(path):
    region_details = APIGatewayRegion.get()
    cert_id = get_cert_id_from_path(path)
    result = region_details.client_certificates.get(cert_id)
    if result is None:
        return make_error_response('Client certificate ID "%s" not found' % cert_id, code=404)
    return result
def add_client_certificate(path, data):
    region_details = APIGatewayRegion.get()
    result = common.clone(data)
    result["clientCertificateId"] = cert_id = common.short_uid()
    result["createdDate"] = common.now_utc()
    result["expirationDate"] = result["createdDate"] + 60 * 60 * 24 * 30  
    result["pemEncodedCertificate"] = "testcert-123"  
    region_details.client_certificates[cert_id] = result
    return make_json_response(to_client_cert_response_json(result))
def update_client_certificate(path, data):