Stop suppressing the for-frameworks guard inside umbrella context (#58850)

Summary:
Pull Request resolved: #58850

The for-frameworks guard skipped its warning whenever `RN_UMBRELLA_CONTEXT` was defined, and its message told consumers to include the header through the module umbrella. Neither makes sense for this tier: umbrellas only re-export public headers, and framework-tier modules have no umbrella at all. The exemption therefore had no legitimate use; its only effect was to hide a public header transitively leaking a for-frameworks header into consumer code.

Drop the `RN_UMBRELLA_CONTEXT` exemption so such a leak is reported, and point the message at the only real escape hatch, `RN_ALLOW_FRAMEWORKS`. No umbrella or public header includes a for-frameworks header today, so this does not change any existing build.

Changelog:
[Internal]

___

Differential Revision: D123399815

fbshipit-source-id: 20c3da6dd27163aa644e4a8475815037baa432cf

Author: coado

packages/react-native/ReactCommon/react/cxxstableapi/FrameworksGuard.h

@@ -13,23 +13,25 @@
 //   #include <react/cxxstableapi/FrameworksGuard.h>
 //
 // "For frameworks" headers are APIs intended for framework authors integrating
-// React Native, not for ordinary app code. Including one directly emits a
-// SUPPRESSIBLE warning under enforcement. A framework author acknowledges the
-// usage by defining `RN_ALLOW_FRAMEWORKS`, which silences the warning.
+// React Native, not for ordinary app code. Including one, directly or
+// transitively, emits a SUPPRESSIBLE warning under enforcement. A framework
+// author acknowledges the usage by defining `RN_ALLOW_FRAMEWORKS`, which
+// silences the warning. Module umbrellas never re-export these headers, so
+// `RN_UMBRELLA_CONTEXT` does not suppress the warning: a public header that
+// includes a for-frameworks header leaks it, and is reported.
 //
 // See <react/cxxstableapi/UmbrellaGuard.h> for the full `RN_*` macro contract.
 // In short:
 //   RN_STRICT_API        Consumer opt-in master switch; the guard is inert
 //                        without it.
 //   RN_ALLOW_FRAMEWORKS  Consumer opt-out acknowledging framework-tier usage.
-//   RN_UMBRELLA_CONTEXT  Internal marker set by an umbrella around its includes.
 //   RN_BUILDING          Set by React Native's own build.
 //
 // This header is intentionally NOT `#pragma once`-guarded: it must be
-// re-evaluated on every inclusion so each direct include is checked.
+// re-evaluated on every inclusion so each include is checked.
 // =============================================================================
 
-#if defined(RN_STRICT_API) && !defined(RN_ALLOW_FRAMEWORKS) && !defined(RN_UMBRELLA_CONTEXT) && !defined(RN_BUILDING)
+#if defined(RN_STRICT_API) && !defined(RN_ALLOW_FRAMEWORKS) && !defined(RN_BUILDING)
 #warning \
-    "This is a 'for frameworks' React Native API, intended for framework authors rather than app code. Include it via the module umbrella <React/<Module>.h>, or define RN_ALLOW_FRAMEWORKS to acknowledge framework-tier usage and silence this warning."
+    "This is a 'for frameworks' React Native API, intended for framework authors rather than app code. Define RN_ALLOW_FRAMEWORKS to acknowledge framework-tier usage and silence this warning."
 #endif