We currently run the all test cases in `parallel` category at the same
time, which invokes hundreds process at the same time, and that seems
causing some flakiness in CI. (maybe related to #18487)
This PR limits the concurrency to the number of cpu cores. This is more
aligned to how Node.js run their `parallel` test in their repository.
42c4a35952/Makefile (L356)
This PR adds the remaining ~650 Node.js compat test cases from std/node.
Among these 650 cases, about 130 cases are now failing. These failing
cases are prefixed with `TODO:` in `tests/node_compat/config.json`.
These will be addressed in later PRs.
