...passes the simplest unit test
* create a Several<int>
* populate from `std::initializer_list`
* random-access to elements
''next step would be to implement iteration''
Some decisions
- use a single template with policy base
- population via separate builder class
- implemented similar to vector (start/end)
- but able to hold larger (subclass) objects
At the time of the initial design attempts, I naively created a
classic interface to describe an fixed container allocated ''elsewhere.''
Meanwhile the C++ language has evolved and this whole idea looks
much more as if it could be a ''Concept'' (C++20). Moreover, having
several implementations of such a container interface is deemed inadequate,
since it would necessitate ''at least two indirections'' — while
going the Concept + Template route would allow to work without any
indirection, given our current understanding that the `ProcNode` itself
is ''not an interface'' — rather a building block.
