TM iOS: Move generated specs for OSS NativeModules to github

Summary:
Note: iOS only.

This spec file (.h/.mm) was generated via FB internal codegen tool for TurboModule. The tool itself is not yet ready to be opensourced, but at least the generated file is. The output is based on all the Flow types added via https://github.com/facebook/react-native/issues/24875.
This file can be used by each ObjC NativeModule to be TurboModule compliant.

Reviewed By: rickhanlonii

Differential Revision: D15978911

fbshipit-source-id: 9e97495287bc406e0ed0ccf89cf370753b538772

Libraries/FBReactNativeSpec/BUCK

@@ -0,0 +1,16 @@
+load("//tools/build_defs/oss:rn_defs.bzl", "fb_apple_library", "react_native_xplat_target_apple")
+
+fb_apple_library(
+    name = "FBReactNativeSpec",
+    autoglob = True,
+    contacts = ["oncall+react_native@xmail.facebook.com"],
+    frameworks = [
+        "Foundation",
+        "UIKit",
+    ],
+    deps = [
+        "fbsource//xplat/js/react-native-github:RCTTypeSafety",
+        "fbsource//xplat/js/react-native-github/Libraries/RCTRequired:RCTRequired",
+        react_native_xplat_target_apple("turbomodule/core:core"),
+    ],
+)

tools/build_defs/oss/rn_defs.bzl

@@ -78,6 +78,9 @@ def react_native_target(path):
 def react_native_xplat_target(path):
     return "//ReactCommon/" + path
 
+def react_native_xplat_target_apple(path):
+    return react_native_xplat_target(path) + "Apple"
+
 # Example: react_native_tests_target('java/com/facebook/react/modules:modules')
 def react_native_tests_target(path):
     return "//ReactAndroid/src/test/" + path