CI(benchmarks): make job split consistent across reruns (#6614)

## Problem

We've got several issues with the current `benchmarks` job setup:
- `benchmark_durations.json` file (that we generate in runtime to
split tests into several jobs[0]) is not consistent between these
jobs (and very not consistent with the file if we rerun the job). I.e.
test selection for each job can be different, which could end up in
missed tests in a test run.
- `scripts/benchmark_durations` doesn't fetch all tests from the
database (it doesn't expect any extra directories inside
`test_runner/performance`)
- For some reason, currently split into 4 groups ends up with the 4th
group has no tests to run, which fails the job[1]

- [0] https://github.com/neondatabase/neon/pull/4683
- [1] https://github.com/neondatabase/neon/issues/6629

## Summary of changes
- Generate `benchmark_durations.json` file once before we start
`benchmarks` jobs (this makes it consistent across the jobs) and pass
the file content through the GitHub Actions input (this makes it
consistent for reruns)
- `scripts/benchmark_durations` fix SQL query for getting all required
tests
- Split benchmarks into 5 jobs instead of 4 jobs.

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

@@ -44,6 +44,10 @@ inputs:
     description: 'Postgres version to use for tests'
     required: false
     default: 'v14'
+  benchmark_durations:
+    description: 'benchmark durations JSON'
+    required: false
+    default: '{}'
 
 runs:
   using: "composite"
@@ -160,7 +164,7 @@ runs:
         # 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 "$TEST_OUTPUT/benchmark_durations.json"
+          echo '${{ inputs.benchmark_durations || '{}' }}' > $TEST_OUTPUT/benchmark_durations.json
 
           EXTRA_PARAMS="--durations-path $TEST_OUTPUT/benchmark_durations.json $EXTRA_PARAMS"
         fi