[rpc_binder] Implement RPC binder over init-managed Unix domain socket

This implements an RPC binder over init-managed Unix domain sockets.
The cl adds binder tests and the new API is also used for
vm_payload_service inside Microdroid.
A previous cl aosp/2229557 sets up the binder over anonymous Unix sockets.

Test: atest MicrodroidTests ComposHostTestCases
Bug: 222479468
Change-Id: I0c7c38f4792c4536f5f88eb7e035091505f782f7
diff --git a/libs/binder/tests/binderRpcTestCommon.h b/libs/binder/tests/binderRpcTestCommon.h
index dc7d264..654e16c 100644
--- a/libs/binder/tests/binderRpcTestCommon.h
+++ b/libs/binder/tests/binderRpcTestCommon.h
@@ -69,6 +69,7 @@
     PRECONNECTED,
     UNIX,
     UNIX_BOOTSTRAP,
+    UNIX_RAW,
     VSOCK,
     INET,
 };
@@ -81,6 +82,8 @@
             return "unix_domain_socket";
         case SocketType::UNIX_BOOTSTRAP:
             return "unix_domain_socket_bootstrap";
+        case SocketType::UNIX_RAW:
+            return "raw_uds";
         case SocketType::VSOCK:
             return "vm_socket";
         case SocketType::INET: