[rkpd] Refactor rkpd_client into an independent lib for reuse

This allows rkpd_client to be reused by both keystore2 and
AVF pVM remote attestation.

Test: atest keystore2_test librkpd_client.test
Bug: 241428146
Change-Id: Ibdf95c4deb2ba499daaecd170c2971cda4e80bba
diff --git a/keystore2/Android.bp b/keystore2/Android.bp
index e59b6f2..c378b42 100644
--- a/keystore2/Android.bp
+++ b/keystore2/Android.bp
@@ -58,6 +58,7 @@
         "liblog_rust",
         "libmessage_macro",
         "librand",
+        "librkpd_client",
         "librustutils",
         "libserde",
         "libserde_cbor",