[boost] High number of integer_sequence/index_sequence implementations

Bunch of Boost libraries have their own integer_sequence/index_sequence implementation. Wouldn’t it be better if there was boost::integer_sequence/boost::index_sequence? boost\beast\core\detail\integer_sequence.hpp boost\callable_traits\detail\polyfills\make_index_sequence.hpp boost\context\detail\index_sequence.hpp boost\fusion\support\detail\index_sequence.hpp boost\mp11\integer_sequence.hpp boost\phoenix\core\detail\index_sequence.hpp (alias of fusion one) boost\poly_collection\detail\functional.hpp (uses mp11 one) boost\test\data\index_sequence.hpp boost\variant\detail\multivisitors_cpp11_based.hpp