Right now the DisjointSet implementation only applies in 2 places

• These are two geometry nodes. Except Cycles.

The specificity of nodes is to use int instead of int64_t for indexes, to save memory.
Since nodes are currently the only user of this implementation, it makes sense to
make it a template so that it can be used both in nodes, with memory savings, and
in other modules, if necessary, with an acceptable size for them.