Support manifest fragments.

LOCAL_VINTF_FRAGMENTS/vintf_fragments are
used to specify what manifest fragments should be installed
by a target.

Test: fragments get installed to the right location
Test: broken fragment gets detected
Test: boot device and verify service is working and manifest is updated
Test: verify OTA package contains fragments
Bug: 66917623
Change-Id: I21abe65a31b8c3d255c8ccd80e102ff3acb23105