test_runner: run benchmarks in parallel (#4683)

## Problem

Benchmarks run takes about an hour on main branch (in a single job),
which delays pipeline results. And it takes another hour if we want to
restart the job due to some failures.
 
## Summary of changes
- Use `pytest-split` plugin to run benchmarks on separate CI runners in
4 parallel jobs
- Add `scripts/benchmark_durations.py` for getting benchmark durations
from the database to help `pytest-split` schedule tests more evenly. It
uses p99 for the last 10 days' results (durations).

The current distribution could be better; each worker's durations vary
from 9m to 35m, but this could be improved in consequent PRs.

.github/actions/run-python-test-set/action.yml

@@ -150,6 +150,14 @@ runs:
           EXTRA_PARAMS="--flaky-tests-json $TEST_OUTPUT/flaky.json $EXTRA_PARAMS"
         fi
 
+        # We use pytest-split plugin to run benchmarks in parallel on different CI runners
+        if [ "${TEST_SELECTION}" = "test_runner/performance" ] && [ "${{ inputs.build_type }}" != "remote" ]; then
+          mkdir -p $TEST_OUTPUT
+          poetry run ./scripts/benchmark_durations.py "${TEST_RESULT_CONNSTR}" --days 10 --output "$TEST_OUTPUT/benchmark_durations.json"
+
+          EXTRA_PARAMS="--durations-path $TEST_OUTPUT/benchmark_durations.json $EXTRA_PARAMS"
+        fi
+
         if [[ "${{ inputs.build_type }}" == "debug" ]]; then
           cov_prefix=(scripts/coverage "--profraw-prefix=$GITHUB_JOB" --dir=/tmp/coverage run)
         elif [[ "${{ inputs.build_type }}" == "release" ]]; then