feat(federation): sketch a query completeness correctness check

[goto-bus-stop]

This PR sketches out one way to do a correctness check from when I was working on it, asserting that all the paths requested by the supergraph operation are executed by the query plan. It uses this check on all operations planned in tests.

This is not a complete completeness check and has several limitations that are mentioned in the code comments (and probably some that aren't), but it might hopefully serve as a basis for discussion about what else to do!

It also needs eg. a way to handle @skip/@include conditionals. I think those could be encoded in path elements in this approach.

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[router-perf]

CI performance tests

• connectors-const - Connectors stress test that runs with a constant number of users
• const - Basic stress test that runs with a constant number of users
• demand-control-instrumented - A copy of the step test, but with demand control monitoring and metrics enabled
• demand-control-uninstrumented - A copy of the step test, but with demand control monitoring enabled
• enhanced-signature - Enhanced signature enabled
• events - Stress test for events with a lot of users and deduplication ENABLED
• events_big_cap_high_rate - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity
• events_big_cap_high_rate_callback - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity using callback mode
• events_callback - Stress test for events with a lot of users and deduplication ENABLED in callback mode
• events_without_dedup - Stress test for events with a lot of users and deduplication DISABLED
• events_without_dedup_callback - Stress test for events with a lot of users and deduplication DISABLED using callback mode
• extended-reference-mode - Extended reference mode enabled
• large-request - Stress test with a 1 MB request payload
• no-tracing - Basic stress test, no tracing
• reload - Reload test over a long period of time at a constant rate of users
• step-jemalloc-tuning - Clone of the basic stress test for jemalloc tuning
• step-local-metrics - Field stats that are generated from the router rather than FTV1
• step-with-prometheus - A copy of the step test with the Prometheus metrics exporter enabled
• step - Basic stress test that steps up the number of users over time
• xlarge-request - Stress test with 10 MB request payload
• xxlarge-request - Stress test with 100 MB request payload

[dariuszkuc]

Wondering whether correctness.rs should be under test instead of src?

[goto-bus-stop]

I expect it will be useful to have the correctness module accessible from outside the crate (eg. for use in harness or fuzzing), which is not possible if it's part of the tests