Add possibility to limit maxConcurrentWorkers in workerFarm

[witem]

On virtual machines no limited(limited by os.cpus) workerFarm use many thread and fail with coredump.
Maybe we can add some environment variable for redefine default maxConcurrentWorkers in:

cipm/lib/extract.js

Lines 13 to 16 in 89afe14

	this._workers = workerFarm({
	maxConcurrentCallsPerWorker: 20,
	maxRetries: 1
	}, WORKER_PATH)

More details in: https://npm.community/t/npm-ci-failed-child-send-is-not-a-function/726/8

[witem]

@zkat what you think about this proposal?
Maybe I make PR for this?

[iamrakesh]

Any decision/progress on this ?
open to make PR