[Legend] Legend dot Icon fixed id string breaks a11y tests

[dej611]

Describe the bug
The Legend component is using the DotIcon underneath, which exposes a SVG component with a fixed id string: this leads to multiple DOM nodes with the same id value, which is a problem both in general and at a11y level.

Either remove the id (but it is probably used somewhere else) or assign a configurable/dynamic id to it.

To Reproduce
Steps to reproduce the behavior:

1. Go to https://elastic.github.io/elastic-charts/?path=/story/bubble-chart-alpha--multiple (but any other viz with multiple series will work)
2. Execute this JS code in the console: document.querySelectorAll('#dot-a').length
3. Notice the result being > 1

Expected behaviour
Unique id used in the visualization DOM tree.

Kibana Cross Issues
Kibana Lens issue

Checklist

• every related Kibana issue is listed under Kibana Cross Issues list
• kibana cross issue tag is associated to the issue if any kibana cross issue is present

[nickofthyme]

I think this is a duplicate of #970 which was fixed by #973. Please confirm.

[dej611]

Oh sorry, didn't find #970 while searching. I guess it can be closed then 👍
Waiting for the next release to close it on the Kibana side.