Cover cxxreact:messagequeuethread with Stable API guards (#58401) - #58401

Summary:
Classifies `react/utils:utils` as a public target under the C++ stable API three-tier visibility model. Adds `#include <react/cxxstableapi/UmbrellaGuard.h>` to the module's 22 exported headers and introduces the module umbrella `React/Utils.h`, wiring the guard dependency into BUCK, CMake and CocoaPods and the umbrella into BUCK, CocoaPods, the iOS prebuild header config and the Android prefab export.
Consumers that opt into `RN_STRICT_API` now get an error if they include the module's headers directly, and should include `<React/Utils.h>` instead; without that flag the guards are inert, so no existing build changes behaviour.
Changelog: [Internal]
Differential Revision: D117858212

Summary:
Classifies `cxxreact:jsbigstring` as a public target under the C++ stable API three-tier visibility model. Adds `#include <react/cxxstableapi/UmbrellaGuard.h>` to the target's 2 exported C++ headers and introduces the module umbrella `React/JSBigString.h`, wiring the guard dependency into BUCK, CMake and CocoaPods and the umbrella into BUCK, CMake, CocoaPods, the iOS prebuild header config and the Android prefab export.
Consumers that opt into `RN_STRICT_API` now get an error if they include the target's headers directly, and should include `<React/JSBigString.h>` instead; without that flag the guards are inert, so no existing build changes behaviour.
Under `USE_FRAMEWORKS` the pod now maps its headers relative to `ReactCommon`, so they install under `cxxreact/` inside the built framework rather than at its root. Pods that pick up the framework's `Headers` directory through `install_modules_dependencies` are unaffected. `React-RCTFabric`, `ReactCommon` and `React-NativeModulesApple` pin their own search paths instead and are updated here; pods outside the repository that do the same have to make the equivalent change.
Changelog:
[iOS][Breaking] - Install `React-cxxreact` headers under `cxxreact/` inside its framework when `USE_FRAMEWORKS` is enabled. Pods that include `<cxxreact/...>` without calling `install_modules_dependencies` must add `React_cxxreact.framework/Headers` to `HEADER_SEARCH_PATHS`.
Differential Revision: D119144023

Summary:
Pull Request resolved: react#58401
Classifies `cxxreact:messagequeuethread` as a "for frameworks" target under the three-tier C++ stable API visibility model. Consumers that opt into `RN_STRICT_API` now get a warning if they include its headers directly, which they can acknowledge with `RN_ALLOW_FRAMEWORKS`; without that flag the guards are inert, so no existing build changes behaviour.
Changelog: [Internal]
Differential Revision: D119163883