list-processes command shows processes from other users

We may see processes from other users. For example:
```
sywhang@suwhang-ubuntu:~/diagnostics/src/Tools/dotnet-counters$ dotnet run list-processes
11501 custom-counter [Elevated process - cannot determine path]
1120 dotnet /home/sywhang/dotnet/dotnet
11158 dotnet [Elevated process - cannot determine path]
11171 dotnet [Elevated process - cannot determine path]
11188 dotnet [Elevated process - cannot determine path]
11748 dotnet /home/sywhang/dotnet/dotnet
11803 dotnet /home/sywhang/dotnet/dotnet
30112 dotnet [Elevated process - cannot determine path]
30125 dotnet [Elevated process - cannot determine path]
30142 dotnet [Elevated process - cannot determine path]
```

We should probably add a separate command or an option that lets users specify to filter out processes that doesn't belong to the user.