cpuset: use Union-Find to optimize the merging of cpumasks

The process of constructing scheduling domains
 involves multiple loops and repeated evaluations, leading to numerous
 redundant and ineffective assessments that impact code efficiency.

Here, we use union-find to optimize the merging of cpumasks. By employing
path compression and union by rank, we effectively reduce the number of
lookups and merge comparisons.

Signed-off-by: Xavier <xavier_qy@163.com>
Signed-off-by: Tejun Heo <tj@kernel.org>