fs_mgr: replace DM_TABLE_STATUS use with libdm.

This change introduces a new GetTableStatus method on DeviceMapper,
which returns a vector of information about each target in a device's
table. Some target types (such as verity) can also return additional
information as a string.

Support for this call has also been added to the "dmctl" tool via a
"table" command. Examples:

    $ dmctl create blah zero 0 8000 linear 8000 1000 /dev/block/sdd1 0
    $ dmctl table blah
    Targets in the device-mapper table for blah:
    0-8000: zero
    8000-9000: linear

    For verity:
    sailfish:/ # dmctl table system
    Targets in the device-mapper table for system:
    0-4128792: android-verity, V

Bug: 110035986
Test: libdm_test gtest; AVB1 device still boots
Change-Id: Iaf13450d3b32e2264c7c399a8af8d6bade260592
5 files changed