[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/rialto/tests/test.rs b/rialto/tests/test.rs
index 6a6dcf4..ee7ecb4 100644
--- a/rialto/tests/test.rs
+++ b/rialto/tests/test.rs
@@ -77,8 +77,9 @@
     info!("Received response: {response:?}.");
 
     match response {
-        Response::GenerateEcdsaP256KeyPair(EcdsaP256KeyPair { maced_public_key, .. }) => {
-            assert_array_has_nonzero(&maced_public_key[..]);
+        Response::GenerateEcdsaP256KeyPair(EcdsaP256KeyPair { maced_public_key, key_blob }) => {
+            assert_array_has_nonzero(&maced_public_key);
+            assert_array_has_nonzero(&key_blob);
             Ok(maced_public_key)
         }
         _ => bail!("Incorrect response type: {response:?}"),