[QtPositioning] Permission API migration

Migrate module to the new permission API. The primary goal is to move the permission requesting to the application executables, and have the library do just the permission checking.

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The main expected backends needing modification are Android and Darwin (iOS, macOS). In addition to modifying the backends, the module's examples and tests need to migrated as applicable *)

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The change needs to be documented in the module documentation.

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*) Note: at the time of this writing the permissions QML API is not available, which is needed to migrate the QML example apps.