[BUG] Disable UFCS on template function with non-template local (g:=0; x.g<>();)

[JohelEGP]

See #807 (comment):

The one case we can handle is when source local name lookup results in a variable.
If it isn't templated, func<targs>(obj) can't be valid, so the only option is the member call.
See https://cpp2.godbolt.org/z/T6sdezYKh:

t: @struct type = {
  f: <T> (this) = { }
  g: <T> (this) = { }
}
main: () = {
  t().f<int>(); // OK.

  g := 0;
  // error: 'g' does not name a template but is followed by template arguments
  t().g<int>();
  _ = g;
}

auto main() -> int{
  CPP2_UFCS_TEMPLATE(f<int>)(t());// OK.
  auto g {0}; 
  CPP2_UFCS_TEMPLATE(g<int>)(t());// S
  static_cast<void>(std::move(g));
}

main.cpp2:10:22: error: 'g' does not name a template but is followed by template arguments
   10 |   CPP2_UFCS_TEMPLATE(g<int>)(t());
      |                      ^~~~~~
raw.githubusercontent.com/hsutter/cppfront/main/include/cpp2util.h:855:84: note: expanded from macro 'CPP2_UFCS_TEMPLATE'
  855 | #define CPP2_UFCS_TEMPLATE(...)                           CPP2_UFCS_(&,(),template,__VA_ARGS__)
      |                                                                                    ^~~~~~~~~~~
raw.githubusercontent.com/hsutter/cppfront/main/include/cpp2util.h:845:51: note: expanded from macro 'CPP2_UFCS_'
  845 |   noexcept(CPP2_UFCS_IS_NOTHROW_ARG(QUALID,TEMPKW,__VA_ARGS__)) CPP2_FORCE_INLINE_LAMBDA -> decltype(auto) \
      |                                                   ^~~~~~~~~~~
raw.githubusercontent.com/hsutter/cppfront/main/include/cpp2util.h:803:90: note: expanded from macro 'CPP2_UFCS_IS_NOTHROW_ARG'
  803 | #define CPP2_UFCS_IS_NOTHROW_ARG(QUALID,TEMPKW,...)   CPP2_UFCS_IS_NOTHROW(QUALID,TEMPKW,__VA_ARGS__)
      |                                                                                          ^~~~~~~~~~~
raw.githubusercontent.com/hsutter/cppfront/main/include/cpp2util.h:801:60: note: expanded from macro 'CPP2_UFCS_IS_NOTHROW'
  801 |               requires noexcept(CPP2_UFCS_REMPARENS QUALID __VA_ARGS__(std::declval<Obj>(), std::declval<Params>()...)); }
      |                                                            ^~~~~~~~~~~
main.cpp2:8:8: note: non-template declaration found by name lookup
    8 |   auto g {0}; 
      |        ^