Add seconds to human_time_diff()

[johnjamesjacoby]

When using human_time_diff() any difference less than 1 minute will appear as:

• 1 min

Disregarding that "min" should probably be "minutes", I propose we add support for seconds, using the MINUTE_IN_SECONDS constant.

This could be:

• 1 second
• 2 seconds
• or even less than 1 minute

[swissspidy]

See also: #29849

[pento]

35655.diff​ Refreshes the original patch and adds a unit test.

[pento]

In 45573:

Formatting: Add support for seconds to human_time_diff().

The web has gotten so much faster since human_time_diff() was created, we need to be able to measure time differences with much finer granularity. Now, we can.

Props johnjamesjacoby, pento.
Fixes #35655.