Fix cost result filtering for custom metrics

[tninesling]

When filtering a metric by a demand control cost value, the metric would never be published. This was uncovered when someone was trying to go through our demand control quickstart.

The root of the problem is that custom supergraph metrics are being deserialized to a SupergraphValue::Custom, and that always converts to an Instrument with an increment of Increment::Custom. During on_response, histograms with this increment type are thrown away if they are empty. The fix is to make sure that cost selectors are converted to an Instrument with Increment::EventCustom.

Separately, I set up a test for a similar case where we try to filter results by cost delta, which still did not work after this fix. The root of this separate issue was that float and integer attributes were considered incomparable. I have updated the implementation of PartialOrd for AttributeValue to convert integers into floats to do this comparison. This allows users to intuitively use integers in comparisons with selectors that may select float values.

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Checklist

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• Changes are compatible¹
• Documentation² completed
• Performance impact assessed and acceptable
• Tests added and passing³
  • Unit Tests
  • Integration Tests
  • Manual Tests

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Notes

Footnotes

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2. Configuration is an important part of many changes. Where applicable please try to document configuration examples. ↩

3. Tick whichever testing boxes are applicable. If you are adding Manual Tests, please document the manual testing (extensively) in the Exceptions. ↩

[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