Add GPU memory stats to SystemMemory atom

On S+ devices we started tracking GPU driver mem allocations.
Record the allocations in the SystemMemory atom (pulled periodically and at LMK time)

Given the GPU memory overlaps with ion allocations do not (yet) account for it in untracked memory calculations

Test: manual
Bug: 149462065
Change-Id: I8cc09d7240ccf0fecd1bab1f62e8daf352edd8ea