Something in-between a memory pool and an object pool. Lock-free, header only, primarily intended for C++17 but might also compile with C++14.
A pool is created from a sequence of fixed sizes in ascending order unless using mem::PoolSuitableFor<...> in which
case you can simply dump all your types you're going to use with the pool as template arguments regardless of ordering
or possible duplicates of sizes. See pool_test.cpp for examples.
When allocating, the pool finds the most suitable size for a given object type during compilation. Relies on std::max_align_t. All methods in mem::Pool must be called from the
same thread, but a mem::PoolPtr obtained through Pool::MakeUnique() or a std::shared_ptr obtained through
Pool::MakeShared() can be marshalled to any other thread and die wherever they want.