Replace boost with std

[matthew-reynolds]

Part of #403.

Replaces all usages of boost w/ std equivalents available since C++11 or C++14.

• boost::recursive_mutex -> std::recursive_mutex
• boost::mutex -> std::mutex
• boost::T::scoped_lock -> std::lock_guard<T> (See note 1)
• boost::bind -> std::bind
• boost::ptr_vector<T> -> std::vector<T*> (See note 2)
• boost::lexical_cast<double> -> std::stod

Note 1: boost::T::scoped_lock is just a typedef for boost::unique_lock<T>. I could have used the corresponding std::unique_lock<T>, but for our usage, std::lock_guard<T> is fully equivalent and may have slightly less overhead. std::scoped_lock supersedes std::lock_guard, but is only available in C++17.

Note 2: Although boost::ptr_vector offers a lot of functionality/optimizations that std::vector doesn't, in our case we're just holding pointers until they are destructed, we never do anything with them, so we don't care about these differences.

[matthew-reynolds]

~CI failure looks to be unrelated to these changes. One of the builds passed, one failed during install of realtime_tools~

Edit: Thanks to whoever restarted that failed build :)