test: the row-identity lock out of SQL's reach, bulk_parallel_writer by hand, and the row_lock_buckets bound (#1341 items 55, 56, 16) - #1415

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/