fix(bridge_query_planner): change log level for mismatches

[lrlna]

When using experimental_query_planner_mode:both, emit mismatch metrics as debug rather than warn as there are still a fair few mismatches.

[github-actions]

@lrlna, please consider creating a changeset entry in /.changesets/. These instructions describe the process and tooling.

[router-perf]

CI performance tests

• step - Basic stress test that steps up the number of users over time
• reload - Reload test over a long period of time at a constant rate of users
• step-with-prometheus - A copy of the step test with the Prometheus metrics exporter enabled
• events_without_dedup_callback - Stress test for events with a lot of users and deduplication DISABLED using callback mode
• no-tracing - Basic stress test, no tracing
• events - Stress test for events with a lot of users and deduplication ENABLED
• events_without_dedup - Stress test for events with a lot of users and deduplication DISABLED
• 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
• xlarge-request - Stress test with 10 MB request payload
• const - Basic stress test that runs with a constant number of users
• 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
• step-jemalloc-tuning - Clone of the basic stress test for jemalloc tuning
• xxlarge-request - Stress test with 100 MB request payload
• demand-control-uninstrumented - A copy of the step test, but with demand control monitoring enabled
• events_callback - Stress test for events with a lot of users and deduplication ENABLED in callback mode
• large-request - Stress test with a 1 MB request payload
• demand-control-instrumented - A copy of the step test, but with demand control monitoring and metrics enabled