Summary

This PR changes the way the X-axis is rendered in linear bar charts.
Instead of computing the ticks as

new Array(Math.floor((nicePaddedDomain[1] - nicePaddedDomain[0]) / minInterval) + 1)
            .fill(0)
            .map((_, i) => nicePaddedDomain[0] + i * minInterval);

I've converted this code to use the standard d3.scale.ticks instead.

This causes a lot of failures in the VRTs because a lot of bar chart uses the Linear scale on the x axis (that should be discouraged if not used in association with the histogram mode or with a controlled number of ticks)

The changes at the screenshot levels are also due to the reverting nature to ordinal scale in the X axis of bar chart and the subsequent removal of the legend extra parameter.

As discussed also with @monfera a bar chart can use the linear scale on the x scale, but its use slightly distorts the nature of the reading: in this case, the bar is only an adornment of a Y value and its width doesn't represent any more an interval in the x scale unless you use the histogram mode that correctly aligns the ticks at the beginning and end of the bar interval.

Checklist

• The proper chart type label has been added (e.g. :xy, :partition)
• The proper feature labels have been added (e.g. :interactions, :axis)
• All related issues have been linked (i.e. closes #123, fixes #123)
• The proper documentation and/or storybook story has been added or updated
• Visual changes have been tested with all available themes including dark, light, eui-dark & eui-light