[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/binderRpcUniversalTests.cpp b/libs/binder/tests/binderRpcUniversalTests.cpp
index 1e8d93d..f960442 100644
--- a/libs/binder/tests/binderRpcUniversalTests.cpp
+++ b/libs/binder/tests/binderRpcUniversalTests.cpp
@@ -86,7 +86,7 @@
 
     SocketType type = std::get<0>(GetParam());
     if (type == SocketType::PRECONNECTED || type == SocketType::UNIX ||
-        type == SocketType::UNIX_BOOTSTRAP) {
+        type == SocketType::UNIX_BOOTSTRAP || type == SocketType::UNIX_RAW) {
         // we can't get port numbers for unix sockets
         return;
     }