### 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/
API_PATH_LAMBDA_PROXY_BACKEND_ANY_METHOD = "/lambda-any-method/foo1"
    API_PATH_LAMBDA_PROXY_BACKEND_ANY_METHOD_WITH_PATH_PARAM = "/lambda-any-method/{test_param1}"
    API_PATH_LAMBDA_PROXY_BACKEND_WITH_IS_BASE64 = "/lambda-is-base64/foo1"
    
    TEST_STREAM_KINESIS_API_GW = "test-stream-api-gw"
    TEST_STAGE_NAME = "testing"
    TEST_LAMBDA_PROXY_BACKEND = "test_lambda_apigw_backend"
    TEST_LAMBDA_PROXY_BACKEND_WITH_PATH_PARAM = "test_lambda_apigw_backend_path_param"
    TEST_LAMBDA_PROXY_BACKEND_ANY_METHOD = "test_lambda_apigw_backend_any_method"
    TEST_LAMBDA_PROXY_BACKEND_ANY_METHOD_WITH_PATH_PARAM = (
        "test_lambda_apigw_backend_any_method_path_param"
    )
    TEST_LAMBDA_PROXY_BACKEND_WITH_IS_BASE64 = "test_lambda_apigw_backend_with_is_base64"
    TEST_LAMBDA_SQS_HANDLER_NAME = "lambda_sqs_handler"
    TEST_LAMBDA_AUTHORIZER_HANDLER_NAME = "lambda_authorizer_handler"
    TEST_API_GATEWAY_ID = "fugvjdxtri"
    TEST_API_GATEWAY_AUTHORIZER = {
        "name": "test",
        "type": "TOKEN",
        "providerARNs": ["arn:aws:cognito-idp:us-east-1:123412341234:userpool/us-east-1_123412341"],
        "authType": "custom",
        "authorizerUri": "arn:aws:apigateway:us-east-1:lambda:path/2015-03-31/functions/"
        + "arn:aws:lambda:us-east-1:123456789012:function:myApiAuthorizer/invocations",
        "authorizerCredentials": "arn:aws:iam::123456789012:role/apigAwsProxyRole",
        "identitySource": "method.request.header.Authorization",
        "identityValidationExpression": ".*",
        "authorizerResultTtlInSeconds": 300,
    }
    TEST_API_GATEWAY_AUTHORIZER_OPS = [{"op": "replace", "path": "/name", "value": "test1"}]
    def test_create_rest_api_with_custom_id(self):