Is your feature request related to a problem? Please describe.
The replacement of vislib requires also a replacement of the current functional tests available in Kibana.
These tests are checking also the rendering capabilities inside Kibana picking and analyzing DOM elements.
With the current @elastic/charts library, rendering in Canvas, this is no more possible.

Describe the solution you'd like

• find and collect every PageObject functions, used by functional tests in Kibana, that are checking values/variables in the DOM rendered by vislib
• analyze these functions and extract a set of possible replacement properties/statistics that can be extracted from the chart state or chart selectors (e.g. number of bars, lines, areas, points, bars values, colors, etc)
• put those statistics into the available <ChartStatus/> component as attributes only when the debug flag is enabled
• enable the debug flag in vislib only when running on the CI (we should be careful here because the debug currently also enable the graphical debug that can break Kibana visual regression tests)
• replace the PageObject functions for vislib with similar tests using our exposed statistics/properties
• where possible, extract from the functional tests the chart state (in particular the specs configurations) and create a set of VRTs in the elastic-charts repo to check the correctness of the rendering.

Describe alternatives you've considered
Enable Percy on Kibana, but we should define when we want to run it and how

Related issue in Kibana: elastic/kibana#70176