report: add cpu info to report output

The report shows CPU consumption %, but without the number of CPU cores,
a consumer cannot tell if the percent (given across all cores) is
actually problematic. E.g., 100% on one CPU is a problem, but 100% on
four CPUs is not necessarily.

This change adds CPU information (similar to `os.cpus()`) to the report
output. Extra info besides the count is also provided as to avoid future
breaking changes in the eventuality that someone needs it; changing the
datatype of `header.cpus` would be breaking.

PR-URL: https://github.com/nodejs/node/pull/28188
Refs: https://github.com/nodejs/diagnostics/issues/307


Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>