An option to always display the value on each legend item

[angorayc]

There is no value for each legend item unless hovering on the chart - Could we have the option to display the value on each legend item

Example
At the moment, no value show on legend item by default

Value of each legend item only show on hovering the chart:

Expected
Could we show the sum of the bucket by default, and it display the value of the selected bucket while users hovering on the chart.

[elasticmachine]

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

[markov00]

A bit more context: the value rendered in the legend represent the following:

• when your mouse is over the chart, it shows the values that are projected on the X axis
• if the current cursor position doesn't have data, the legend doesn't show data
• if the cursor is outside the chart then the legend will show the last bucket of data, only if there is data

The way to fix this should include:

• add the ability to specify a legend title to describe what the number means on every state
• define a way to specify the value to show, that can be (a data point value, an aggregation, etc)

[ninoslavmiskovic]

This is also related to the "The metric in the tooltip" issue: #106024

[stratoula]

Closing as duplicate of #16096