iOS: update to use the new Logger class

Last year, Apple introduced a new Logger class to unify logging: https://developer.apple.com/videos/play/wwdc2020/10168/

The current implementation works for now, but maybe it is a good idea to switch for future compatibility.

Start by reviewing the Apple WWDC 2020 Logger presentation linked in the issue, then locate the current iOS logging implementation in the repository. Determine the affected logging entry points and replace the existing approach with Apple's Logger class; done means iOS logging uses the new class without breaking current behavior.

Written by the indexing model from the issue text.