单个应用允许多少个基于区域的 UILocalNotifications
How many region based UILocalNotifications are allowed for single app
苹果 Doc 说：
Apps are limited in the total number of regions they may monitor at
any given time, and local notifications configured with a region value
count against that total.
但是total number没有指定，如何知道应用可以监控的总区域数的限制。
根据 Apple 的规定，每个应用的数量限制为 20 个 Location and Maps Programming Guide：
Be judicious when specifying the set of regions to monitor. Regions
are a shared system resource, and the total number of regions
available systemwide is limited. For this reason, Core Location limits
to 20 the number of regions that may be simultaneously monitored by a
single app. To work around this limit, consider registering only those
regions in the user’s immediate vicinity.
苹果 Doc 说：
Apps are limited in the total number of regions they may monitor at any given time, and local notifications configured with a region value count against that total.
但是total number没有指定，如何知道应用可以监控的总区域数的限制。
根据 Apple 的规定，每个应用的数量限制为 20 个 Location and Maps Programming Guide：
Be judicious when specifying the set of regions to monitor. Regions are a shared system resource, and the total number of regions available systemwide is limited. For this reason, Core Location limits to 20 the number of regions that may be simultaneously monitored by a single app. To work around this limit, consider registering only those regions in the user’s immediate vicinity.