Add interface for retrieving partition information

[TheMarex]

We need a class for #3350 that will be the interface to the query algorithm and the customize algorithm:

When talking about node and edge ID this will refer to the IDs of the Edge-Based-Graph stored in the .ebg file.

Some pseudo code of a possible interface:

class MultiLevelPartition
{
// Returns the ID of the cell of `node` at `level`
CellID GetCellID(NodeID node, LevelID level);

// Returns the ID of the level in which `node` is relevant for our query
// That is the lowest level in which node is not in the same cell as start or target
LevelID GetQuerryLevelID(NodeID start, NodeID target, NodeID node);

std::size_t GetNumberOfLevels() const = 0;

std::size_t GetNumberOfCells(LevelID level) const = 0;
};

The data for this class will be provided by the partitioner outlined in #3204.

CellID can be either continuous or not. The latter enables compact packing into a 32bit integer, the former makes the data structure to look up the actual cells more memory efficient.

[TheMarex]

Going to use a previous implementation for this.