Support Android SDK 35

[devPalacio]

Cleaning up some compiler errors and deprecations when building against the Android API 35 JAR (compileSDK = 35)

e: DbxOfficialAppConnector.kt:296:35 Not nullable value required to call an 'iterator()' method on for-loop range
e: DropboxAuthIntent.kt:21:68 Only safe (?.) or non-null asserted (!!.) calls are allowed on a nullable receiver of type ApplicationInfo?

applicationInfo returning null is now handled properly.

Added some branching to use non-deprecated package signature APIs for devices >= API 28