Improve container information

Container information printed to hs-err files and VM.info is very useful. Some important numbers are still missing though:

v1:
- memory+swap usage
- kernel memory usage
- arguably, kmem limit, even though kernel may not adhere to it

I do not care much for the limit of kernel memory, but others might.

v2:
- swap current usage, possibly swap max usage

In addition, I'm not sure, but maybe the current interface for V2 is somewhat wrong in reporting v2 "swap" numbers as "memory+swap". In V2, "swap" is, AFAICS, pure swap. That is different from V1, where swap was memory + swap. See also https://www.kernel.org/doc/html/latest/admin-guide/cgroup-v2.html:

```
The combined memory+swap accounting and limiting is replaced by real control over swap space.

The main argument for a combined memory+swap facility in the original cgroup design was that global or parental pressure would always be able to swap all anonymous memory of a child group, regardless of the child’s own (possibly untrusted) configuration. However, untrusted groups can sabotage swapping by other means - such as referencing its anonymous memory in a tight loop - and an admin can not assume full swappability when overcommitting untrusted jobs.
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