ANDROID: Incremental fs: Add status to sysfs

Adding seven sysfs entries per mount:

reads_failed_timed_out
reads_failed_hash_verification
reads_failed_other
reads_delayed_pending
reads_delayed_pending_us
reads_delayed_min
reads_delayed_min_us

to allow for status monitoring from userland

Change-Id: I50677511c2af4778ba0c574bb80323f31425b4d0
Test: incfs_test passes
Bug: 160634343
Bug: 184291759
Signed-off-by: Paul Lawrence <paullawrence@google.com>