Provide the kernel, machine, CPU Model, hostname, and Node.js version
fields to SystemInfo and display them in the Web UI. These were added
as metrics exposed to prometheus in b46efeb.
There are more pieces of information about a system than just its CPU,
Memory and disk metrics. To avoid having to build a separate collection
and subscription for metrics and system info, rename the existing system
metrics to system info in anticipation of providing additonal static
system information such as CPU model in it.
