Add a BackendUnifiedServiceManager wrapper

This can be directly used by java and rust ffi
Test: atest aidl_integration_test
Bug: 333854840
Flag: EXEMPT refactor

Change-Id: I12c3730a89422bf08ab723a82888431f291bd7b3
diff --git a/libs/binder/Android.bp b/libs/binder/Android.bp
index f31f8d3..1abde5c 100644
--- a/libs/binder/Android.bp
+++ b/libs/binder/Android.bp
@@ -442,8 +442,10 @@
     name: "libbinder_kernel_defaults",
     srcs: [
         "BufferedTextOutput.cpp",
+        "BackendUnifiedServiceManager.cpp",
         "IPCThreadState.cpp",
         "IServiceManager.cpp",
+        "IServiceManagerFFI.cpp",
         "ProcessState.cpp",
         "Static.cpp",
         ":libbinder_aidl",
@@ -519,7 +521,6 @@
         "ParcelableHolder.cpp",
         "PersistableBundle.cpp",
     ],
-
     target: {
         android: {
             // NOT static to keep the wire protocol unfrozen