Log metrics for RKP fallback event.

This CL adds metrics logging for fallback during RKP hybrid mode.

Test: atest com.android.remoteprovisioner.unittest.ServerToSystemTest#testFallback
on cuttlefish, followed by ./statsd_testdrive 10124
Bug: 194510784
Change-Id: I3d6184df02828fef1d0110688afe1ba2db10eae9
(cherry picked from commit 400b225c94329c5192695c15bd2f81568fc92f5e)
diff --git a/keystore2/src/remote_provisioning.rs b/keystore2/src/remote_provisioning.rs
index 40c06e5..a19462b 100644
--- a/keystore2/src/remote_provisioning.rs
+++ b/keystore2/src/remote_provisioning.rs
@@ -43,7 +43,9 @@
 use crate::database::{CertificateChain, KeystoreDB, Uuid};
 use crate::error::{self, map_or_log_err, map_rem_prov_error, Error};
 use crate::globals::{get_keymint_device, get_remotely_provisioned_component, DB};
+use crate::metrics_store::log_rkp_error_stats;
 use crate::utils::watchdog as wd;
+use android_security_metrics::aidl::android::security::metrics::RkpError::RkpError as MetricsRkpError;
 
 /// Contains helper functions to check if remote provisioning is enabled on the system and, if so,
 /// to assign and retrieve attestation keys and certificate chains.
@@ -189,6 +191,7 @@
                         ),
                         e
                     );
+                    log_rkp_error_stats(MetricsRkpError::FALL_BACK_DURING_HYBRID);
                     Ok(None)
                 }
                 Ok(v) => match v {