Add Keystore 2.0 service.

This patch adds a boilerplate Keystore 2.0 service. It is configured to
run on the device but does not provide any useful service yet.
It provides basic functionality for generating, importing and using
keys, but it still lacks full Keystore functionality.

Test: VtsKeystore2V1_0TargetTest (in followup CL)
Bug: 160623310
Bug: 160930114
Bug: 160930117
Bug: 160930331
Bug: 159465122
Change-Id: I7dfa2f2f63f4da3af620aff2ec99c0cba3bda6fd
7 files changed