Fix rapl subdomain only added once

[weriomat]

Closes #70

[root@cpl siomon]# ./target/release/sio sensors
── cpu/rapl ──
  RAPL dram-0                                5.8 W
  RAPL dram-1                                5.8 W
  RAPL dram-2                                5.0 W
  RAPL dram-3                                4.0 W
  RAPL package-0                            52.0 W
  RAPL package-1                            57.0 W
  RAPL package-2                            49.7 W
  RAPL package-3                            51.0 W

We now take the first integer we find which should be the domain and append it to the RAPL subdomain name.

[root@cpl powercap]# cat /sys/class/powercap/intel-rapl:0:0/name
dram -> dram-0
[root@cpl powercap]# cat /sys/class/powercap/intel-rapl:3:0/name
dram -> dram-3

[weriomat]

On a side note, this change will affect single NUMA systems as well.

$ ls /sys/class/powercap/
intel-rapl  intel-rapl:0  intel-rapl:0:0
$ cat /sys/class/powercap/intel-rapl:0:0/name
core
$ sudo ./target/release/sio --direct-io --no-nvidia sensors
...
── cpu/rapl ──
  RAPL core-0                                1.1 W
  RAPL package-0                            32.8 W
...

If we want to have the name as core on a single NUMA system we could first look if we have multiple NUMA domains and decide based on that information if we need to append the RAPL domain number.

[weriomat]

Renamed parse_subdomain into parse_domain.