Method create_root_node

include/UTL/profiler.hpp:616–625

    std::thread::id thread_id        = std::this_thread::get_id();

    NodeId create_root_node() {
        const NodeId prev_node_id = this->current_node_id;
        this->current_node_id     = NodeId::root; // advance to a new node

        this->mat.grow_nodes();
        this->mat.prev_id(this->current_node_id) = prev_node_id;
        // link new node backwards, since this is a root the prev. one is empty and doesn't need to link forwards

        return this->current_node_id;
    }

    NodeId create_node(CallsiteId callsite_id) {
        const NodeId prev_node_id = this->current_node_id;