output group order is different from cli

Currently, it seems that the output results from critcmp are sorted by time, with faster groups appearing first. However, this might not be consistent with the order specified in the CLI, which could be confusing. Perhaps there could be an option to follow the order from the CLI or place the fastest group first.

```
critcmp ~/Downloads/benchcmp2.json ~/Downloads/master.json
group benchcmp2_cecf96b9 master
----- ------------------ ------
bufvec/manual_chunk 1.01 4.3±0.02µs ? ?/sec 1.00 4.3±0.02µs ? ?/sec

critcmp ~/Downloads/benchcmp2.json ~/Downloads/0.0.1.json
group 0.0.1 benchcmp2_cecf96b9
----- ----- ------------------
bufvec/manual_chunk 1.00 4.3±0.03µs ? ?/sec 1.00 4.3±0.02µs ? ?/sec
```
[data.json.zip](https://github.com/BurntSushi/critcmp/files/14082006/data.json.zip)

Start by reproducing the two critcmp commands in the issue with the attached data.json.zip, then trace the CLI output-ordering entry point. Determine how groups are currently sorted and clarify whether the intended behavior is CLI order, fastest-first, or a selectable option. Done means the chosen ordering is implemented and covered by a regression test.

Written by the indexing model from the issue text.