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/workflows/build_and_test.yml

@@ -396,13 +396,11 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
+        pytest_split_group: [ 1, 2, 3, 4 ]
         build_type: [ release ]
     steps:
       - name: Checkout
         uses: actions/checkout@v3
-        with:
-          submodules: true
-          fetch-depth: 1
 
       - name: Pytest benchmarks
         uses: ./.github/actions/run-python-test-set
@@ -411,9 +409,11 @@ jobs:
           test_selection: performance
           run_in_parallel: false
           save_perf_report: ${{ github.ref_name == 'main' }}
+          extra_params: --splits ${{ strategy.job-total }} --group ${{ matrix.pytest_split_group }}
         env:
           VIP_VAP_ACCESS_TOKEN: "${{ secrets.VIP_VAP_ACCESS_TOKEN }}"
           PERF_TEST_RESULT_CONNSTR: "${{ secrets.PERF_TEST_RESULT_CONNSTR }}"
+          TEST_RESULT_CONNSTR: "${{ secrets.REGRESS_TEST_RESULT_CONNSTR }}"
       # XXX: no coverage data handling here, since benchmarks are run on release builds,
       # while coverage is currently collected for the debug ones