switch to `process.getActiveResourcesInfo()` in node v16.14.0+

Node v16.14.0 includes `process.getActiveResourcesInfo()` ([docs](https://nodejs.org/api/all.html#all_process_processgetactiveresourcesinfo), [PR](https://github.com/nodejs/node/pull/40813)) as a public alternative to `process._getActiveHandles()` and `process._getActiveRequests()`. We use the latter two in "lib/metrics/runtime.js". We should use the blessed new one when able.