Refactors in advance of crypto-secure boot level

Various refactors that set the stage for a future change to make
max-boot-level keys cryptographically secure.

Bug: 176450483
Test: keystore2_test
Change-Id: I4e4e91ae23991131610c7a40f6d347ddcd528ac7
diff --git a/keystore2/src/database.rs b/keystore2/src/database.rs
index 174a928..6a07716 100644
--- a/keystore2/src/database.rs
+++ b/keystore2/src/database.rs
@@ -3025,7 +3025,7 @@
     where
         F: Fn(&Uuid, &[u8]) -> Result<()> + Send + 'static,
     {
-        let super_key = Arc::new(SuperKeyManager::new());
+        let super_key: Arc<SuperKeyManager> = Default::default();
 
         let gc_db = KeystoreDB::new(path, None).expect("Failed to open test gc db_connection.");
         let gc = Gc::new_init_with(Default::default(), move || (Box::new(cb), gc_db, super_key));