mon, mgr: do not output network ping stats

mon, mgr: do not output network ping stats

When doing PG dump using 'ceph pg dump --format json-pretty'
the output is extremely big that the command hangs and also
the ceph-mgr hangs and eventuall fails over.

The exact size depends on the number of OSDs in the cluster
and the number of peers for each OSD.

In tests, it's been identified that the network ping times
is the largest component in terms of size which is removed
from the output now so as to limit the overall size.

Fixes https://tracker.ceph.com/issues/57460

Signed-off-by: Ponnuvel Palaniyappan <pponnuvel@gmail.com>