iOS: Add Ti.Geolocation constant "ACCURACY_REDUCED" support to iOS 13 and older

Summary:
As of Titanium 9.2.0, we added Ti.Geolocation constant ACCURACY_REDUCED which is only supported on iOS 14 and higher. Attempting to use it on older iOS versions will cause a crash. This is by design, but it would better to support this constant on older iOS versions to make the permission handling code easier to write.

Proposal:
On iOS versions older than 14, Titanium should fallback to using ACCURACY_LOW when Ti.Geolocation.accuracy is assigned the ACCURACY_REDUCED constant. This is the closest equivalent.

Note:
We plan on adding all of the iOS only accuracy constants to Android via ticket TIMOB-28117 for parity.