App available memory not tracked in platform context because can't import Obj-C header

[matus-tomlein]

To calculate the available memory statistic that is added in platform context, the tracker used the os_proc_available_memory() API provided on iOS. However, accessing this API requires that the Obj-C header for #include <os/proc.h> is added to the project.

This is not possible under the current project setup as SPM does not allow mixed Swift and Obj-C code in one target. I don't see any easy workarounds at the moment. We could add another Obj-C target to the project that would only surface this information and would be imported by the Swift target.

As of now, the information is not tracked in the v5 tracker.