[air/output] Improve passed time display

[krfricke]

Why are these changes needed?

Includes #34788

This changes the formatting of the total running time like this:

Trial easy_objective_b12ae_00003 completed training after 5 iterations at 2023-05-02 14:46:11. Total running time: 4d 3hr 20min, 2s

Trial easy_objective_d3d85_00008 completed training after 5 iterations at 2023-05-02 14:47:09. Total running time: 4d 0hr 20min 2s

Trial easy_objective_cbd93_00007 finished iteration 5 at 2023-05-02 14:46:56. Total running time: 20min 2s

Trial easy_objective_14e6b_00001 completed training after 5 iterations at 2023-05-02 14:48:58. Total running time: 1hr 0min 2s

It does not turn metrics (e.g. time_this_iter or total_time_s) into written sentences, as this will make it harder to identify these metrics for configuration purposes.

Related issue number

Closes #34922

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[scottsun94]

Thanks!

1. Let's get rid of the comma and only have a space between different units? Something like 4d 3hr 20min 2s
2. For seconds, 02.35s looks really weird.
   • When it's < 1 min, can we use 2.35s (If it's too complicated, maybe it's also okay to show 2s?)
   • When it's > 1 min, round it to integer and show 20min 2s

[krfricke]

Thanks!

1. Let's get rid of the comma and only have a space between different units? Something like `4d 3hr 20min 2s`

2. For seconds, `02.35s` looks really weird.
   
   * When it's < 1 min, can we use `2.35s` (If it's too complicated, maybe it's also okay to show `2s`?)
   * When it's > 1 min, round it to integer and show  `20min 2s`

Makes sense! Let's go for integer seconds everywhere. I don't think there is too much value in having subsecond accuracy.

[scottsun94]

LGTM. Thanks!

[richardliaw]

FYI i'm not really a fan of the human-readable time, but that's ok for now. let's leave it to the users to decide.

[gjoliver]

nice. just a couple of nits.