Googletest export

Mark ACTION_Pn()-generated functions as must-use-result.

This catches when a client creates an action and discards it, thinking that the action has actually been applied to something.

This will help people who make the mistake of defining, for example, both `void Use(Foo*)` and `ACTION(Use) { Use(arg); }` for later application to a Foo.  With such an overload, a client may then write `Use();`, forgetting the param and being confused why nothing happens.

This also catches when a client defines their own action in terms of an ACTION()-generated one, invokes the ACTION's builder, and then fails to invoke the resulting action, thinking it's operating on the outer action's parameters.

PiperOrigin-RevId: 312108101

googlemock/include/gmock/gmock-actions.h

@@ -1512,6 +1512,7 @@ auto InvokeArgumentAdl(AdlTag, F f, Args... args) -> decltype(f(args...)) {
       return_type gmock_PerformImpl(GMOCK_ACTION_ARG_TYPES_AND_NAMES_) const; \
     };                                                                        \
   };                                                                          \
+  inline name##Action name() GTEST_MUST_USE_RESULT_;                          \
   inline name##Action name() { return name##Action(); }                       \
   template <typename F>                                                       \
   template <GMOCK_ACTION_TEMPLATE_ARGS_NAMES_>                                \