[docs] Document the inotify/max_user_watches requirements

[ader1990]

Description

When deploying K8S with a large set of services, including especially Rook/Ceph and Kubevirt on the same cluster, containers that heavily use inotify start erroring out.

Nowdays, the Linux kernel sets the max_user_watches max number to 1048576, and in the [8192, 1048576] range according to the RAM size.
See: torvalds/linux@9289012

It would be nice to document this behaviour and suggest setting a bigger value in case of large K8S deployment (with an Ignition Butane example).

cat /proc/sys/fs/inotify/max_user_instances
cat /proc/sys/fs/inotify/max_user_watches

See: https://www.suse.com/support/kb/doc/?id=000020048

[jepio]

@ader1990 how about we document this and ship a default sysctl setting that is good enough for a decently sized cluster?