VSD: Expose aggregate DORA performance score values in API

For DORA scores based on metrics, they will be aggregated for potentially many projects. For users looking at potentially thousands of projects, these need to be aggregated into counts of projects with the various scores for each key metric.

group / scores / counts (low, med, high)

Identify a GraphQL API structure that can allow the flexibility of taking a set of projects and return an aggregate of those scores. Return the number of projects in each category (low, med, high) of each of the 4 DORA key metrics.

• Not including subgroups vs including subgroups
• Only specific projects by ID vs all
• Subset of projects by topic
• Subset of projects by name/description (existing search logic)
• Between a set of dates (within 180 day range)

And of course any set would pass through authorisation, though the ProjectsFinder would do that for us.

Broken off #386844 (closed).