test: enable trace-events tests for workers

Use the `cwd` option for `child_process` instead of `process.chdir()`
to enable the trace events tests to run on workers.

PR-URL: https://github.com/nodejs/node/pull/23698
Refs: https://github.com/nodejs/node/pull/23674#discussion_r225335819


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>