[VSA] Change Total time chart (previously "days to completion") to lead time and cycle time

Problem

• "Days to completion for all stages" is a roundabout way of saying "lead time".
• The current scatterplot is not an appropriate chart for something with so much content
• It would be nice to see cycle time and lead time superimposed

Proposal

• Replace scatterplot for a line chart in the overview section this will be part of #346554 (closed)
• Use cycle time and lead time
• Add tooltips with the definition of cycle time and lead time
• Align on definitions of lead time and cycle time

TODO

• backend VSA Endpoints for lead/cycle time as time serie... (#361746 - closed)
• frontend Rename the chart to "Lead time and Cycle time"
• frontend Update the chart to use the values from the new lead / cycle time endpoint(s)
• Add tooltips with the definition of cycle time and lead time ??

See also this Figma file →