[Meta] Legacy editors deprecation plan

[teresaalvarezsoler]

We are aiming to deprecate and fully remove the legacy editors (TSVB and Aggregation based -including Timelion-) in version 10.0 (~2.5 years from now) assuming users can replace their visualizations with Lens that should support any key missing features by then.

This is a meta issue to track all the tasks that need to happen:

• Show TSVB and Agg based as "legacy" when users create a visualization from the library #191489
• Remove the options to create new TSVB and Agg based visualizations in 9.0 #197045
• Gathering advanced telemetry with visualization configs #197702
• Identify and agree on a list of key missing features that need to be added into Lens or Dashboards
• Design a migration strategy to Lens
• Implement key missing features
• Implement migration strategy
• Show a deprecation badge each time a visualization is open in edit mode letting users know the deprecation date
• Remove legacy editors

[elasticmachine]

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