Describe the feature:
Update the Lens/Agg-based visualizations to use a fixed legend by default

Describe a specific use case for the feature:
When I'm building a dashboard with multiple vertically arranged visualizations (common)
I need legend size to default to a fixed size instead of auto
So I can avoid having to set legend size on every visualization to get a consistent layout

Design questions: CC @gvnmagni @MichaelMarcialis

• What size should be default? Medium? Any concerns?