[Hex] Use libhex to encode hex string in libs/apkverify/v4.rs

Bug: 239413416
Test: Refactoring code. Existing unit tests are sufficient.
Change-Id: I13fd87f4f881d3103069b7d99b1bea3b45d36699
diff --git a/libs/apkverify/Android.bp b/libs/apkverify/Android.bp
index 78192d2..1862820 100644
--- a/libs/apkverify/Android.bp
+++ b/libs/apkverify/Android.bp
@@ -33,6 +33,7 @@
     name: "libapkverify.test",
     defaults: ["libapkverify.defaults"],
     test_suites: ["general-tests"],
+    rustlibs: ["libhex"],
     data: ["tests/data/*"],
 }