Keystore 2.0: Move test utils to separate library.

Move TempDir test utils to separate library for easier reuse.

Test: keystore2_test
Change-Id: If1edfde39b66efa43f8a5ed32a500fad57291512
diff --git a/keystore2/src/database.rs b/keystore2/src/database.rs
index 344fe2f..225378f 100644
--- a/keystore2/src/database.rs
+++ b/keystore2/src/database.rs
@@ -1792,7 +1792,7 @@
     };
     use crate::key_perm_set;
     use crate::permission::{KeyPerm, KeyPermSet};
-    use crate::test::utils::TempDir;
+    use keystore2_test_utils::TempDir;
     use android_hardware_security_keymint::aidl::android::hardware::security::keymint::{
         HardwareAuthToken::HardwareAuthToken,
         HardwareAuthenticatorType::HardwareAuthenticatorType as kmhw_authenticator_type,