metrics: replace gosigar with gopsutil (#21041)

* replace gosigar with gopsutil

* removed check for whether GOOS is openbsd

* removed accidental import of runtime

* potential fix for difference in units between gosig and gopsutil

* fixed lint error

* remove multiplication factor

* uses cpu.ClocksPerSec as the multiplication factor

* changed dependency from shirou to renaynay (#20)

* updated dep

* switching back from using renaynay fork to using upstream as PRs were merged on upstream

* removed empty line

* optimized imports

* tidied go mod