[refactor] Split the message macro in a standalone library for reuse

This simplifies the task of creating an independent library of
rkpd_client later.

Test: atest keystore2_test
Bug: 241428146
Change-Id: Idddf37d14580e691fde5a494e54297465cb693b6
diff --git a/keystore2/src/lib.rs b/keystore2/src/lib.rs
index 8c08d3e..e51a319 100644
--- a/keystore2/src/lib.rs
+++ b/keystore2/src/lib.rs
@@ -28,7 +28,6 @@
 pub mod id_rotation;
 /// Internal Representation of Key Parameter and convenience functions.
 pub mod key_parameter;
-pub mod ks_err;
 pub mod legacy_blob;
 pub mod legacy_importer;
 pub mod maintenance;
@@ -51,3 +50,5 @@
 mod super_key;
 mod sw_keyblob;
 mod watchdog_helper;
+
+use message_macro::source_location_msg as ks_err;