[Lens][TSVB] Add support for default fields in convert to lens

[rajvi-ptl]

Describe the feature:
The "Convert to lens" feature will be added at the dashboard level in 8.7.0. This feature does not migrate TSVB visualizations that have not configured time_field.

Describe a specific use case for the feature:
The "Convert to lens" feature helps to migrate visualizations to the lens at the dashboard level. But for TSVB visualization, if time_field is not configured, it won't show the "Convert to lens" option. Although, after selecting time_field the "Convert to lens" will appear.

Before configuring time_field:

After configuring time_field:

[elasticmachine]

Pinging @elastic/kibana-visualizations @elastic/kibana-visualizations-external (Team:Visualizations)

[dej611]

I guess we could do something if we know the data view used. What do you think @stratoula ?

Edit
Tried to reproduce the issue but I couldn't. The default time field is already set when available for a time-based dataView and if the control is not set TSVB will render this error:

Was that a dataView with no default time field set? What's the rest of the TSVB time series configuration?

[stratoula]

I guess it is a TSVB that works on the deprecated index pattern mode.

[stratoula]

@rajvi-crest I can't reproduce it

Can you share more info? Was it a migrated TSVB visualization? What have you configured on the data panel??

[rajvi-ptl]

@rajvi-crest I can't reproduce it

Can you share more info? Was it a migrated TSVB visualization? What have you configured on the data panel??

When we try converting panels from existing dashboards (for example ActiveMQ), it won't show option Edit visualisation in lens. But if we will click on the time field and select @timestamp field then the Edit visualisation in lens option will be available on top.

This is happening in imported/integration's dashboard only. As the "time_field" value is empty in the json file of dashboard.

[stratoula]

Closing this as we cant reproduce it