Runs, events and metered interactions

Counts the organisation's runs started in the window and the events those runs recorded, by type, plus how many runs are active now. The window defaults to the current UTC calendar month to date and may span at most 92 days. Where unified billing runs, billing adds the organisation's rig.interaction meter for the current billing period (the UTC calendar month, whatever the window) from the billing ledger: the free allowance, how many interactions were used and are reserved, and the charge so far before tax. One interaction is one accepted inbound email, inbound callback or mock exchange with its response; a transport retry carrying the same identity (an email's Message-ID with the same bytes, a callback's Idempotency-Key or Webhook-Id with the same request) counts once, so used can be below the event counts. Creating projects, suites, runs and resources, faults, replays, waits, reads and assertions are never metered. billing is null where interactions are not metered. Reading usage is never metered. Needs rig.read.