Keystore 2.0: km_compat: Implement getKeyCharacteristics.

Ignore-AOSP-First: No automerge path from AOSP.
Bug: 188848331
Bug: 187862706
Test: keystore2_km_compat_test
Change-Id: Ib54916c4f5f4960a82d6e8695aa8b8caa085a2de
Merged-In: Ib54916c4f5f4960a82d6e8695aa8b8caa085a2de
2 files changed