Secretkeeper: more VTS tests

Add tests for:
- large number of session creations
  - also use a bigger identity, to better simulate real use
- attempt to retrieve a secret with an incorrect identity

Test: VtsSecretkeeperTargetTest (shiba)
Bug: 327526008
Change-Id: I8dddf643d03a8fb679511564cb03c2248477c116
diff --git a/security/secretkeeper/aidl/vts/Android.bp b/security/secretkeeper/aidl/vts/Android.bp
index b9ce5ce..be07a7b 100644
--- a/security/secretkeeper/aidl/vts/Android.bp
+++ b/security/secretkeeper/aidl/vts/Android.bp
@@ -27,6 +27,7 @@
         "libciborium",
         "libcoset",
         "libdiced_open_dice",
+        "libhex",
         "liblog_rust",
         "libsecretkeeper_client",
     ],