Add probe tier to `--list_probes`

[Erick Galinkin]

Summary

When enumerating probes, also print the tier of the probe. Alternately/additionally, allow --list_probes to accept an optional argument to list only probes of that tier.

Basic example

garak --list_probes yields something like:

probes: ansiescape 🌟                       
probes: ansiescape.AnsiEscaped.      Tier 1
probes: ansiescape.AnsiRaw.              Tier 2
...

garak --list_probes 1 yields something like:

probes: ansiescape.AnsiEscaped.      Tier 1
probes: dan.Ablation_Dan_11_0.         Tier 1

etc.

Motivation

Help people identify/search for probes a little more cleanly.

[Nakul Rajpal]

@erickgalinkin May I be assigned this role? My plan for the issue is as follows:

1. Read the existing Garak CLI + update to allow for second parameter with function
2. Extend the logic to allow tier to be printed based on the second parameter.
3. Add help text and filtering