YT-CPPHGL-24: Prepare the HGL module documentation

[SpectraL519]

• Added documentation comments to the public API elements of the HGL module
• Prepared the tutorial pages and images for the HGL module's documentation
• Extended the groups.dox file with HGL module's group definitions
• Moved the hypergraph property algorithms to a dedicated file: `hgl/algorithm/properties.hpp"
• Aligned the implementation of the undirected hypergraph projection to properly handle single-vertex hyperedges (convert them into self-loops)