Usage metrics for 2023.5 about entity updates from submissions and conflicts

[ktuite]

Closes getodk/central#498

Adds

• num_entity_updates_sub (total and recent) entity updates via submission
• num_entity_updates_api (total and recent) entity updates via api
  • the two above sum together to get the previous metric num_entity_updates
• num_entities_updated (total and recent) counts the entities updated rather than the update events
  • can be used to figure out what fraction of all entities ever get updated, and then with the update frequencies, how many updates each has on average
• num_entity_conflicts entities that have ever had a conflict
  • how common are conflicts in general?
• num_entity_conflicts_resolved entities that have ever had a conflict that are currently resolved
  • do people use entities with conflicts without resolving them?

What has been done to verify that this works as intended?

tests, trying it on a test analytics server

Why is this the best possible solution? Were any other approaches considered?

How does this change affect users? Describe intentional changes to behavior and behavior that could have accidentally been affected by code changes. In other words, what are the regression risks?

Does this change require updates to the API documentation? If so, please update docs/api.md as part of this PR.

Before submitting this PR, please make sure you have:

• run make test-full and confirmed all checks still pass OR confirm CircleCI build passes
• verified that any code from external sources are properly credited in comments or that everything is internally sourced

[matthew-white]

Looks great!