Respect user default (NSUserDefaults) for MGLCollisionBehaviorPre4_0 Info.plist key

[samfader]

This is more of a feature request so I've changed the template around:

The request

With the MGLCollisionBehaviorPre4_0 Info.plist key added here (#12941), app developers can now set this key to determine cross-source collision behavior. However, there is no way to set this key at the developer level (NSUserDefaults).

I know there is some discussion as to why this choice was made here, but it would be useful to those wrapping the iOS SDK to have a user-controlled option here as well.

[1ec5]

However, there is no way to set this key at the user level (NSUserDefaults).

NSUserDefaults is something of a misnomer. The only practical difference between Info.plist keys and NSUserDefaults settings is that the latter can be set at runtime, whereas the former is static – it can only be set at build time and can’t differ from device to device. With the Info.plist key, a wrapper of this SDK would have no control over the setting.

[1ec5]

Fixed in #13426.