[LOCOKIT] Logging to file

[sobri909]

There's enough going on that it LocoKit needs its own logging to file, especially with the scheduled background tasks, that do things away from Xcode debug sessions.

iOS 15's OSLog looks viable, apart from the iOS 15 requirement. Need to work out something standard-ish and workable in the short term. Possibly just migrate upstream Arc Mini/v3's logging code, which uses an Apple blessed framework anyway.

Todos

• Migrate to Logger
• Use OSLog and friends to reading to file. Nope. They're too immature for this use case still.
• Migrate Mini's DebugLogging wrapper to LocoKit, wrapping system Logger