Add compatibility wrapper

This implements the Keymint 1 spec by wrapping the legacy Keymaster
implementation.

Test: atest keystore2_km_compat_test
Test: atest keystore2_certificate_test
Test: Manually verify that keystore2 can find a legacy implementation.
Change-Id: Ia56c25eed0f97a7e6194954a655ceb62259b3273
12 files changed