Add digest support and implementation name to getHardwareFeatures

This is needed to support the keystore statistics gathering initiative.
It will allow us to get information about what kinds of keymaster
implementations exist in the ecosystem, and which ones fail in which
ways.

Bug: 36549319
Test: Will add to VTS tests
Change-Id: I49ee4623656060d69a6de7723b11cd715150451a
3 files changed