Add 60 new C++ questions covering modern C++ features (#7182)

Fixes #5111

This PR adds 60 comprehensive C++ questions (Q161-Q220) covering:
- C++11 features: move semantics, smart pointers, lambdas, auto, constexpr
- C++14 features: make_unique, std::exchange, generic lambdas
- C++17 features: structured bindings, std::optional, std::variant, std::any, if constexpr, fold expressions, std::filesystem
- C++20 features: concepts, three-way comparison, std::span
- STL algorithms: transform, accumulate, find, sort, copy, remove_if
- Threading: std::atomic, std::mutex, std::future, std::async
- Type traits: enable_if, is_same, decay, conditional
- Utilities: std::function, std::bind, std::invoke, std::apply

All questions include:
- Detailed explanations
- Code examples
- Official C++ reference documentation links
- Coverage of modern C++ best practices

Total additions: 903 lines of educational content addressing the need for modern C++ questions.

Author: 0xsatoshi99