Add Unsafe based storage backend

Summary:
@public

Adds another version of property storage for `YogaNode`, using `sun.misc.Unsafe`.

Adopts the stub concept from Litho for `Unsafe`, as it is hidden by the Android SDK.

Reviewed By: pasqualeanatriello

Differential Revision: D9140103

fbshipit-source-id: a4b376eca341b724a00f873467ae8bf8eaac69f4

java/BUCK

@@ -29,9 +29,19 @@ yoga_cxx_library(
     ],
 )
 
+yoga_java_library(
+    name = "stubs",
+    srcs = glob(["stubs/**/*.java"]),
+    source = "1.7",
+    target = "1.7",
+)
+
 yoga_java_library(
     name = "java",
     srcs = glob(["com/facebook/yoga/*.java"]),
+    provided_deps = [
+        ":stubs",
+    ],
     required_for_source_only_abi = True,
     source = "1.7",
     target = "1.7",