Add interfaces required by smart idle maintenance service

Added interfaces required by smart idle maintenance service in
StorageManagerService, whose goal is to determine when to trigger
filesystem defragmentation while keeping the best user experience
as long as possible, and avoiding hurting UFS lifetime.

Test: check smart idle maintenance log every hour
Bug: 202283480
Bug: 181079477
Signed-off-by: Daeho Jeong <daehojeong@google.com>
Change-Id: I012cfb9b01e5d21ec71700c3c52ac9c096cd1a90