[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/binderRpcTestFixture.h b/libs/binder/tests/binderRpcTestFixture.h
index 721fbfe..5a78782 100644
--- a/libs/binder/tests/binderRpcTestFixture.h
+++ b/libs/binder/tests/binderRpcTestFixture.h
@@ -108,7 +108,8 @@
     bool supportsFdTransport() const {
         return clientVersion() >= 1 && serverVersion() >= 1 && rpcSecurity() != RpcSecurity::TLS &&
                 (socketType() == SocketType::PRECONNECTED || socketType() == SocketType::UNIX ||
-                 socketType() == SocketType::UNIX_BOOTSTRAP);
+                 socketType() == SocketType::UNIX_BOOTSTRAP ||
+                 socketType() == SocketType::UNIX_RAW);
     }
 
     void SetUp() override {