Reduce truncation of information in the runningProcesses*.txt files (#12398)
Reduce truncation of information in the runningProcesses*.txt files (#12398)

- widen lines in process dump files
- increase process dump frequency to once every 2 minutes (from 5 minutes)
- simplify process dump filenames
  - no need to keep files from previous ./build.ps1 invocations around
  - by definition, job isn't hung if it can move to next build step
- save previous process dump files
  - should help if cancellation kills processes before final process dump runs

nits:
- move from deprecated `Get-WmiObject` to `Get-CimInstance`
- trim trailing whitespace
aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore