Allow selection of time field in DIscover/saved search

[markwalkom]

Describe the feature: Related - #1714

Be able to select a timestamp in Discover/a saved search and that over writes the default one - ie it allows you to remove the default from the table.

Describe a specific use case for the feature: I have a dataset that has 5 timestamps. Event submission, start, finish, actioned and updated. But I can only ever really set Discover, and any subsequent saved searches, to use the primary time field for the pattern.

If I want to use one of the other time fields as the primary I need to end up having two time fields, which is counter intuitive and ends up looking messy.

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[kertal]

So when we get rid of the legacy table we intend to make also the time field to be removable from the table, however this solves just one issue you mentioned, you want to choose another time field as primary, so when you would create a Visualization that field should be used?

[timroes]

Let's keep this issue to only track switching the "primary" time field (if we'd want that) in Discover. Lens already supports using any time field to do auto date histograms on. If discover would support switching the primary time fields, we might want to add a hint to the VISUALIZE_FIELDS trigger to allow specifying which date field should be used as primary one, so Lens could take that into account when navigating to it.

[kertal]

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.