Summarize results in the index

Provide an overview of the results for each run by showing some aggregated counters by deployment type, listing the number of executed testcases, how many of them are automated vs. manual, and pass/skip/fail/incomplete counters.

Do this with a single SQL query returning a nested JSON structure with all the data in it.

This moves some complexity from Python code to a relatively large but not overly complex SQL query.

As a shortcut, the SQL query uses the Postgres-specific DISTINCT ON syntax to keep things simple and fast.

Here's the new rendered version used by the screenshot test, even if it's not very representative as it only gives an hint of the way results are grouped rather than actually showing it: