`AlgorithmResult` improvement suggestions

[ljeub-pometry]

• group_by should return groups as lists of nodes instead of transforming to string names
• would be nicer if groups were returned as our own object instead of a hash map so we can have additional methods such as .as_subgraphs?
• the internal HashMap uses usize instead of VID which complicates things for no reason
• get_all seems useless?

[miratepuffin]

Adding other tickets which can go in here - #910 #1000 #1007 #1155