keystore2: rename MonotonicRawTime to BootTime

Due to https://r.android.com/2822970 ("Use CLOCK_BOOTTIME for keystore2
auth token received time"), MonotonicRawTime now uses CLOCK_BOOTTIME
instead of CLOCK_MONOTONIC_RAW.  Therefore, rename it to BootTime.

Bug: 309686873
Test: atest -p --include-subdirs system/security/keystore2
Change-Id: If1fbbac2eccb03dc7360ae742d79e58f871fb80d
diff --git a/keystore2/src/globals.rs b/keystore2/src/globals.rs
index 0f899ed..eb755a6 100644
--- a/keystore2/src/globals.rs
+++ b/keystore2/src/globals.rs
@@ -23,7 +23,7 @@
 use crate::legacy_importer::LegacyImporter;
 use crate::super_key::SuperKeyManager;
 use crate::utils::watchdog as wd;
-use crate::{async_task::AsyncTask, database::MonotonicRawTime};
+use crate::{async_task::AsyncTask, database::BootTime};
 use crate::{
     database::KeystoreDB,
     database::Uuid,
@@ -68,7 +68,7 @@
 
     DB_INIT.call_once(|| {
         log::info!("Touching Keystore 2.0 database for this first time since boot.");
-        db.insert_last_off_body(MonotonicRawTime::now());
+        db.insert_last_off_body(BootTime::now());
         log::info!("Calling cleanup leftovers.");
         let n = db.cleanup_leftovers().expect("Failed to cleanup database on startup.");
         if n != 0 {