[DevOps Adoption] Add totals line to "trend over time" graph

Overview

A trend over time graph was added to DevOps Adoption in #337561 (closed). The graph shows columns for Dev Sec and Ops. An aggregation of all features would provide visibility into the overall trends in an organization's devops journey.

Summary

• Add a blue line to the graph that shows the total adoption (percentage of the total number of features for all of Dev, Sec, Ops).
• Match the blue color to the blue for "Overall adoption" in the section higher on the page.
• Add the blue line to the legend with a label "Total adoption"

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