use resident, not virtual for memory usage

[digi-owl]

Right now OSMonitor use virtual size when sorting by memory usage.

This however include various memory pages that are not in active use, or shared across multiple processed (shared libraries etc).

resident is the size the process is actively using.

[eolwral]

I have checked the source, actually it uses resident memory now, but the rank still isn't prefect, because it should use private dirty memory, unfortunately the API doesn't support on old Android version, I will keep use resident memory until I deprecate the old Android version.

[digi-owl]

ok. Figured it was using something else as it was reporting much higher ram pr process than Android settings (and the OSMonitor memory shows 3 unlabeled entries). My apologies for the noise.