[Feat][C++] Replace the polymorphism implement of EdgesCollection

[acezen]

Is your feature request related to a problem? Please describe.
Currently GraphAr use variant to implement the EdgesCollection polymorphism, it's clear for API access but it's hard to convert to the actual EdgesCollection like:

auto& edges = GraphAr::ConstructEdgesCollection(AdjListType::ordered_by_source).value()
if (adj_list_type==AdjListType::ordered_by_source) {
    auto real_edges = std::get<>(edges)
    ... // process code
} else {
   auto real_edges = std::get<>(edges)
   ... // same process code
}

Describe the solution you'd like
Use inherit and virtual member function to implement the polymorphism

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
Add any other context or screenshots about the feature request here.

[acezen]

The PR #238 has been merged, close