OS Metrics dashboard has missleading info on the CPU and Memory section

[vponomaryov]

scylla-version=2024.1
monitoring-version=4.6.0
dashboard=OS-2024-1

Screenshot:

Problems:

1. The CPU and memory info is located under the Network parent header. Why?
2. The left bottom graph called Available memory contains GB/s on the vertical axis.
   The vertical axis must not have anything per second, because the horizontal one is the time.
3. The 2 bottom graphs both called Available memory. It is confusing.
   Maybe left one must be Available memory in Gb or Available memory (abs) ?
   And right one maybe must be Available memory (%)