Implement CarStorageMonitoringManager::getAggregateIoStats

This API allows callers to gather the current running total of I/O metrics happening on the system.

Bug: 65846699
Bug: 32512551
Test: bit CarServiceTest:com.android.car.CarStorageMonitoringTest
Change-Id: Ibc0f58ff4fbb1a1fe9ea9c2fff52db7a1b74b99a
6 files changed