Implement traits on std types

[danakj]

• [x] Try for std::optional https://github.com/chromium/subspace/pull/302
• [ ] Try for std::expected (C++23...)
• [x] FromIterator for std containers https://github.com/chromium/subspace/pull/293
• [x] FromIterator for std::string from chars https://github.com/chromium/subspace/pull/307
• [ ] Extend for std containers
• [ ] Extend for std::basic_string
• [ ] Concat and Join for std::span, std::array and std::vector?
• [ ] Concat and Join for std::basic_string?
• [ ] ... more

I think IntoIterator will be out of scope, it is best positioned as a method, we have sus::iter::from_range() for it.

This requires moving the concept to follow the Concept+Impl+Functions pattern like Try and FromIterator, which I will need to document properly.