Upon source hash validation failure, log ext4 remount information

When source hash verification fails, check if the current partition
is an ext4 that has been remounted.
Log mount count and date.

Based on corresponding functionality in recovery.

Bug: 72074823
Test: manual - Confirm that remount count is present in the log when
      installing an update and the system has been remounted

Change-Id: I3cf12c9f93fa5ef9f73f0a1b6a795eb2a3e9335e