Allow `port`, `protocol` and `fallback` properties in `LoggingConfig`

Hello,

For local developing, I’m creating a mock server for the Cloud Logging API. To use the mock server, I need to specify a custom API endpoint, port, protocol and enable REST fallback.

It appears the `Logging` class constructor doesn't expose options for this. However, the underlying clients it uses (like `LoggingServiceV2Client`) are initialized with `google-gax`'s `ClientOptions`, which supports `apiEndpoint`, `port`, `protocol`, and `fallback`.

Could you please consider exposing these properties in `LoggingConfig`? This would make it much easier to mock the service for local development and testing.

Thanks you.