Function make_test_topo 

pub fn make_test_topo(
    nr_nodes: usize,
    llcs_per_node: usize,
    cores_per_llc: usize,
    hts_per_core: usize,
) -> (Topology, usize)

Build a synthetic Topology with the specified dimensions.

Returns (topology, total_cpu_count). CPU IDs are assigned sequentially starting from 0: node 0’s LLCs get the lowest IDs, then node 1, etc.

Sets the Cpumask test width override to total_cpus so that all masks created during the test have consistent width.