[SDK][iOS] Release v4.5.0

Add a sync channel: the SDK can now keep installation, user and in-app popup data in sync with the WonderPush servers, including opportunistic syncs on access token calls and late resolution of user identifiers. It is active by default and can be turned off
Use synced user data in segmentation, and merge synced popups into the in-app message engine
Give your app code public access to the synced user payload
Report more information about the device's reachability on API and measurement calls
Fix date comparisons in segmentation: field values are now converted to dates when compared against a date criterion
Various fixes to the sync engine
The minimum deployment target is now iOS 15
CocoaPods is no longer supported: this version is not published to CocoaPods Trunk, and future versions will not be either. Use Swift Package Manager or the attached Binaries.zip (xcframeworks)