RCTDeprecation BUCK integration (facebook#41417)

Summary:

Changelog: [Internal]

BUCK boilerplate to integrate the first RCTFoundation library. decided to split this up so we can reference it easily in the future when adding new libs

Differential Revision: D51101009

packages/react-native/ReactApple/Libraries/RCTFoundation/RCTDeprecation/Exported/RCTDeprecation.h

@@ -0,0 +1,16 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#ifndef RCT_DEPRECATED_DECLARATIONS
+#define RCT_DEPRECATED_DECLARATIONS 0
+#endif
+
+#if RCT_DEPRECATED_DECLARATIONS
+#define RCT_DEPRECATED __attribute__((deprecated))
+#else
+#define RCT_DEPRECATED
+#endif

packages/react-native/ReactApple/Libraries/RCTFoundation/RCTDeprecation/README.md

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+RCTDeprecation contains C macros to identify deprecated APIs at build-time.