[Legend] Better usage of space when stats are enabled and legend is positioned either at top or bottom

[dej611]

Describe the issue

Take a legend with a long enough list of stats displayed:

The name column is taking half of the space no matter what to render and the stats is taking the remaining space.
If the stats table is filled enough it can overflow on the right.

It is possible to reproduce also in the charts storybook with a long list of stats: https://elastic.github.io/elastic-charts/storybook/?path=/story/legend--tabular-data&globals=toggles.showHeader:true;toggles.showChartTitle:false;toggles.showChartDescription:false;toggles.showChartBoundary:false;theme:light

Expected behaviour
A better usage of screen space?

[gvnmagni]

Interesting, thank you for pointing this out Marco, we should probably revisit a bit our column logic here which I don't fully remember but I do recall a conversation about it