[gen] oar-properties: add new scheme for pyxis

On pyxis: all cpuset ids (of all threads) a grouped by CPUs:
CPU0: 0-127
CPU1: 128-255

Among a CPU, threads are given in round robin:
CPU0: 0,32,64,96 -> 31,63,95,127
CPU1: 128,160,192,224 -> 159,191,223,255

So looking at the first thread of each core, this give 2 groups:
CPU0: 0-31
CPU1: 128-159
Thus a gap between the 2.

So the new formula to give the first thread id of each core is the
following:
row[:cpuset] = cpu_num * cpu_thread_count + core_num