New column for LXC containers name using the CGroups

[jb-boin]

Fixed the issues listed on https://github.com/htop-dev/htop/issues/216.

I feel like there should be a break to exit the while loop parsing each line of the CGroup file if the LXC container name has been found and if the CGroup column is not used (or at least skip the LXC part if both columns are used and the LXC name has been found). But it seems that the CGroup files are always parsed even if the CGroup column is not used which is not ideal.

[ser]

it would be cool to have it as we have now incus.

[BenBE]

@jb-boin Would you mind updating this PR to base off the latest commit from main? Also AFAICS there are still several open discussion items that should be addressed.

NB: Regarding the lengthy CGROUP names from systemd there's a compressed cgroup (CCGROUP) column. The source for this could be adapted for this feature.