Allow updating location stream settings

[orkun1675]

This PR allows updating the location stream after one is started. It adds a new API endpoint:

  /// Updates the parameters of the active position stream.
  ///
  /// Throws a [NotSubscribedException] when there is no active position stream
  /// to update.
  static Future<void> updatePositionStream({
    required LocationSettings locationSettings,
  }) =>
      GeolocatorPlatform.instance.updatePositionStream(
        locationSettings: locationSettings,
      );

This endpoint allows plugin users to change settings, such as distanceFilter or intervalDuration, without having to stop & start the stream. This is critical if the update is hapenning while the app is in the background since Android does not allow starting a location stream unless the app is in focus.

Fixes https://github.com/Baseflow/flutter-geolocator/issues/1569. Improved version of https://github.com/Baseflow/flutter-geolocator/pull/1406.

If there is interest in merging this PR I will clean it up and send for review.

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Pre-launch Checklist

• [ ] I made sure the project builds.
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• [ ] I updated CHANGELOG.md to add a description of the change.
• [ ] I updated/added relevant documentation (doc comments with ///).
• [ ] I rebased onto main.
• [ ] I added new tests to check the change I am making, or this PR does not need tests.
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