cap threshold sample size at 1 for iai gate

Prevents the default percentage testing of comparing against an average over a window of historical main runs. For iai, the more specific the better, and averages after baselines increases would be too noisy.

Author: yulnr

.github/workflows/benchmarks.yml

@@ -198,6 +198,7 @@ jobs:
               --adapter rust_iai_callgrind \
               --threshold-measure instructions \
               --threshold-test percentage \
+              --threshold-max-sample-size 1 \
               --threshold-upper-boundary 0.01 \
               --ci-only-thresholds \
               --error-on-alert \