chore(federation): remove for_each_element

[goto-bus-stop]

Today's 15-minute cleanup :)

This set of functions is used in one place, and it has some odd behaviours. In JS, an "element" is free, because its data structures are built on element/selection set pairings. But we don't have the "element" type exactly in our data structures, our closest equivalent is the Selection type. Therefore the for_each_element function had to convert types including some inexpensive, but non-zero clones.

for_each_element also translates named fragment spreads to inline fragments. AFAICT, this is a historical artifact ported from JS, as the only place where for_each_element was used does not support named fragment spreads to begin with.

I replaced it, for now, with a manual visitor. I think it might make sense to have something like a for_each_selection API but it's honestly not that much harder to do it manually...

[github-actions]

@goto-bus-stop, please consider creating a changeset entry in /.changesets/. These instructions describe the process and tooling.

[router-perf]

CI performance tests

• 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]

Nice!