Add More Customization to Relative Date Format

[pickypg]

Relates to #13784, but this is a specific example.

Describe the feature:

A field formatter that took the difference from a date field versus now where now is shared (aka the Date Formatter's Relative Date formatter). As a step further though, we should be able to control how fine grained the display is. For example, it currently jumps from "a few seconds ago" to "a minute ago" then minute increments until the hour mark (et cetera). It might be nice to see "15 seconds ago" or even "1 m 15 s ago".

Describe a specific use case for the feature:

When showing log events, it would be nice to see how long ago a certain event occurred and as time passes into hours, it would be nice to get a more exact timeframe.

Elasticsearch does not support this through script fields using Kibana because Elasticsearch intentionally makes it very hard to get ahold of now dynamically (because each shard / field would see a different now, which would be wrong).

We could solve this differently by supporting script params within Kibana (#19716) and providing the ability to tell ES what "now" is at search time, which would allow the script field to do all of this, but that would be a nice to have versus direct UI support.

[elasticmachine]

Pinging @elastic/kibana-app

[ghudgins]

There are interesting workaround ideas using a runtime field to compute this duration...for example this gives you "now" in milliseconds double now = System.currentTimeMillis();

[pickypg]

I would suggest that Kibana provide now as a script parameter rather than try to determine it at runtime from Elasticsearch itself. That provides the most consistent experience and it's much more performant as well.

[ghudgins]

Related issue that should help in visualizations - #112851

[timductive]

Closing this because it's not planned to be resolved in the foreseeable future. It will be tracked in our Icebox and will be re-opened if our priorities change. Feel free to re-open if you think it should be melted sooner.