[Lens] Emphasize dragging/dropping in the same chart dimension will duplicate series

[ghudgins]

Describe the feature:
User picks up field and sees the ability to duplicate the series immediately (drop location appears to the left of the current field) without having to realize they have to drag the field down to the "Drop a field" box to get this functionality. I think this would increase discoverability of this function

Describe a specific use case for the feature:

When I want to create multiple metrics on the same axis filtered different ways
Or multiple metrics for each percentile on the same axis
And I am picking up my existing field on a chart dimension like vertical axis
I need to see a "Duplicate" option appear to the left of my existing field
So I can easily see the field can be duplicated
And it works like it would if I was dragging to another chart dimension (consistency)

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[ghudgins]

This original issue implements the base functionality - this is a usability issue

[markov00]

In order to provide better transparency of priorities, issues that will not be prioritized within the next 24 months are being closed.

Tracking request in Lens general improvements ice box #184459