Add view command to open perfetto trace

[fsimonis]

This PR adds a view commmand that openens a trace in perfetto.
The -c parameter allows passing a json file of startup commands.
The -i parameter can be given multiple ranks, which will then be opened in an isolated workspace. Example -i 0 1 2 to open Ranks 0-2 of all known participants.

The default trace is profiling.pftrace but trace.json is also supported.