Support Keymaster4

This CL changes vold from using a KM3 device directly to using the KM4
support wrapper from the KM4 support library, which supports both KM3
and KM4 devices (KM0, 1 and 2 devices are still supported as well,
because the default KM3 device is a wrapper that uses them).

In addition, I found myself getting confused about which "Keymaster"
types were locally-defined vold keymaster types and which were from
the KM4 HAL and support library, so I changd the approach to
referencing the latter, so all of them are qualified with the "km::"
namespace reference.

Test: Build & boot
Change-Id: I08ed5425641e7496f8597d5716cb3cd0cbd33a7f
8 files changed