Keystore 2.0: Implement APC service.

This patch implements the Android Protected Confirmation service in
Keystore 2.0. This includes a C++ wrapper around the HIDL confirmationui
interface which will stay a HIDL interface for now.
This patch also includes the new AIDL specification.

This patch lacks death listener registration b/176491050.

Bug: 159341464
Bug: 173546269
Test: None
Change-Id: Ida4af108e86b538ab64d1dea4809cfa3b36f74cd
diff --git a/keystore2/src/lib.rs b/keystore2/src/lib.rs
index 5ad77d1..3fb938c 100644
--- a/keystore2/src/lib.rs
+++ b/keystore2/src/lib.rs
@@ -14,6 +14,7 @@
 
 //! This crate implements the Android Keystore 2.0 service.
 
+pub mod apc;
 pub mod auth_token_handler;
 pub mod database;
 pub mod enforcements;