### 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/
region_details = APIGatewayRegion.get()
    api_id = get_api_id_from_path(path)
    validator_id = get_validator_id_from_path(path)
    validator = _find_validator(api_id, validator_id)
    if validator is None:
        return make_error_response(
            "Validator %s for API Gateway %s not found" % (validator_id, api_id),
            code=404,
        )
    result = apply_json_patch_safe(validator, data["patchOperations"])
    entry_list = region_details.validators[api_id]
    for i in range(len(entry_list)):
        if entry_list[i]["id"] == validator_id:
            entry_list[i] = result
    return make_json_response(to_validator_response_json(api_id, result))
def delete_validator(path):
    region_details = APIGatewayRegion.get()
    api_id = get_api_id_from_path(path)
    validator_id = get_validator_id_from_path(path)
    auth_list = region_details.validators[api_id]
    for i in range(len(auth_list)):
        if auth_list[i]["id"] == validator_id:
            del auth_list[i]
            return make_accepted_response()
    return make_error_response(
        "Validator %s for API Gateway %s not found" % (validator_id, api_id), code=404
    )
def handle_validators(method, path, data, headers):