Add smart idle maintenance service

Added 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: Ie7331aec45d62a59b28ca2806e34d6d45b6ffaf4