Reducing dynamic allocations using SSO/SOO

Dynamic allocations can sometimes cause you other trouble than just throwing when you construct objects despite not having enough memory. They often cost you CPU cycles and can cause memory fragmentation. Fortunately, there is a way to protect against it. If you've ever used std::string (post GCC 5.0), you most probably used an optimization called Small String Optimization (SSO). This is one example of a more general optimization named Small Object Optimization (SSO), which can be spotted in types such as Abseil's InlinedVector. The main idea is pretty straightforward: if the dynamically allocated object is small enough, it should be stored inside the class that owns it instead of being dynamically allocated. In std::string's case, usually, there's a capacity, length, and the actual string to store. If the string is short enough (in GCC's case, on 64-bit platforms, it's 15 bytes), it will be stored in some of those...