Include asan options from data partition.

Look for asan options under /data/asan so that multi-process coverage
can be enabled on a newly-started remote process without disabling
verity and without forcing it to be always-on.

Test: adb shell echo "include_if_exists=/data/asan/asan.options.%b" >>
/system/asan.options && adb shell echo
"coverage=1\ncoverage_dir=/data/misc/trace" >
/data/asan/asan.options.android.hardware.light@2.0-service && adb shell killall
android.hardware.light@2.0-service
Bug: 64019182

Change-Id: I241ad8478439323681dc1cfde2fa0770f030ae75