Handle deprecation of top-level comma expression in array subscripts `-Wdeprecated-comma-subscript`

[ManifoldFR]

Support for things like arr[expr1, expr2] has been deprecated in the C++20 standard and is unsupported from C++23.

Indeed this warning crops up on Clang 20:

/home/XYZ/pinocchio/include/pinocchio/bindings/python/collision/broadphase-manager.hpp:35:91: warning: top-level comma expression in array subscript is deprecated in C++20 and unsupported in C++23 [-Wdeprecated-comma-subscript]
   33 |           .def(bp::init<const Model *, const GeometryModel *, GeometryData *>(
      |                ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   34 |             bp::args("self", "model", "geometry_model", "geometry_data"), "Default constructor")
      |             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   35 |                  [bp::with_custodian_and_ward<1, 2>(), bp::with_custodian_and_ward<1, 3>(),
      |                  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
   36 |                   bp::with_custodian_and_ward<1, 4>()])

It seems this mostly concerns the Python bindings when there is some complex lifetime stuff going on.

[ManifoldFR]

Actually this deprecation might have been reverted? https://en.cppreference.com/w/cpp/23.html

It seems there's an actual, official multidimensional subscript operator (that is an operator[] overload). Hopefully this doesn't break Boost.Python? Can't find references to this change on their issue tracker.