[Enhancement proposal]: Return Notification ID (Android)

### Please check the following before submitting a new issue.

- [X] I have searched the [existing issues](https://github.com/baseflow/flutter-geolocator/issues).
- [X] I have carefully [read the documentation](https://github.com/baseflow/flutter-geolocator/blob/main/geolocator/README.md) and verified I have added the required platform specific configuration.

### Please select affected platform(s)

- [X] Android
- [ ] iOS
- [ ] Linux
- [ ] macOS
- [ ] Web
- [ ] Windows

### Proposal

Currently only the channel-name can be set. If the notification needs to be updated, the notification ID is required.

### Pitch

Is it possible to return (or specify) the notification ID when creating `ForegroundNotificationConfig` ?

Start by locating ForegroundNotificationConfig and tracing how Android foreground notifications are created and exposed through the plugin. Determine whether the change should return or accept a notification ID, then identify the existing tests or platform entry points that would verify the ID can be used for updates; the issue names no files or tests.

Written by the indexing model from the issue text.