Expose the sampling rate in the cli to be able to see if it's inconsistent

Currently in the web UI, it's possible to see very easily if the sampling rate is consistent or not by looking at the sample graph in the timeline (the small squares below the activity graph).

For example:

But it's not really possible to see this information in the cli. Usually sampling consistency is a good indication of external machine pressures etc. So it would allow the CLI users to see if the machine is under pressure, or if it can't keep up with the sampling.

We could either have a sparkline graph similar to what we did for the counter information, or we can have a more text based info similar to what we do for the "CPU usage over time".

My guess is that since the sparklines have limited character size, it's going to be difficult to visualize a small gap in the sampling rate, so I think we should start with a text based solution first, and then add the sparkline later if we find it useful.

┆Issue is synchronized with this [Jira Task](https://mozilla-hub.atlassian.net/browse/FP-1366)

Start by locating the CLI output for counter information and the text-based "CPU usage over time" view, then trace how timeline sampling data is exposed to those displays. Done means the CLI presents sampling consistency clearly enough to reveal gaps or external pressure, with coverage for the new output if existing CLI tests are found.

Written by the indexing model from the issue text.