[Lens] Allow reference line text to be rotated in visualizations

[A-Hall]

Describe the feature:

In some situations, the text in reference lines can overlap causing them to be hard or impossible to read. Allowing users to rotate the text 90º would allow for the text to be readable in situations like this.

[elasticmachine]

Pinging @elastic/kibana-vis-editors @elastic/kibana-vis-editors-external (Team:VisEditors)

[markov00]

@flash1293 the label can already be "rotated" ( you are actually rotating the label by 90 degree, but the standard behaviour is to have text labels horizontally laid).
For example you can achieve the following by using the marker code below:

marker={
          <div
            style={{
              position: 'absolute',
              right: 0,
              bottom: 1,
              background: 'rgba(255, 255, 255, 0.5)',
              whiteSpace: 'nowrap',
              textAlign: 'right',
            }}
          >
            horizontal text
          </div>
        }
        markerPosition={Position.Right}

[flash1293]

@markov00 Right, the input required from datavis is more about whether this is the right approach or not. @gvnmagni spent some time thinking about the general issue and how to handle it. Do you have any guidance here, Gio?

[gvnmagni]

I have to admit that I don't have a proper guidance here but I can spend some time trying to see if there is a good solution. My main worries are related to the scalability of the rotated labels (even with just few reference lines we would risk overlapping) and to the amount of space needed to make this to work outside of chart right side limit (causing this chart to be no aligned to other charts in a dashboard). Let me think about this a little and let me see if there is a way to make this work