[rkp] Encrypt/decrypt the private key with AES-256-GCM

This cl implements the private key encryption and decryption
with AES-256-GCM.
The KEK is derived from the sealing CDI with a random salt
generated with TRNG.

The test is added to the busy town config at cl/570947834.

Bug: 279425980
Test: atest rialto_test
Test: atest libservice_vm_requests.test
Change-Id: I214ee37c64cb8508083b02376c8a398ca6049e3b
diff --git a/TEST_MAPPING b/TEST_MAPPING
index adf6309..f5d2dda 100644
--- a/TEST_MAPPING
+++ b/TEST_MAPPING
@@ -99,6 +99,9 @@
       "path": "packages/modules/Virtualization/rialto"
     },
     {
+      "path": "packages/modules/Virtualization/service_vm/requests"
+    },
+    {
       "path": "packages/modules/Virtualization/vm"
     },
     {