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Change ACTION{,_Pn,_TEMPLATE} macros to build functors rather than ActionInterface<> subclasses, thus changing the Action<> wrappers they create to use the modernized (non-const) argument tuple type, allowing these macros to mutate their arguments.

Functor-based Action<>s deep-copy the implementing object, so have the functors use a shared_ptr to the non-trivial state of bound value parameters.  No longer specialize that shared state to the particular action signature, encoding that information instead only in the instantiation of the implementation function.

PiperOrigin-RevId: 341116208