✨ Add transform_reduce on bitset

[elbeno]

Problem:

• It is relatively common to want to do for_each on a bitset, but also capture whether or not the action succeeded at all, e.g. when handling a message with an indexed handler.

Solution:

• Add transform_reduce on bitset.

Note:

• Both for_each and transform_reduce are applicable variadically, however this is not yet implemented. But this is the reason that the bitset is the final argument.
• There are some differences (for the better) from the std::transform_reduce API.
  • The transform function comes before the reduction function. std::transform_reduce is confusing, because the transform happens first but is given second.
  • The type of the init value can be easily given in a template argument; this is helpful for avoiding warnings when passing 0 (an int) to accumulate potentially larger integral types.