[chore] Configure lerna to use npm instead of yarn

[bjoerge]

Looks like hoisting in lerna works with npm again, so I've switched back to using npm as npmClient. Hopefully this will improve overall stability and reduce the daily time spent waiting for the package manager to finish. I'm suspecting we may see a reduction in build times too, as hoisting means better deduping, but haven't tested.

Also tweaked a few other flags, e.g. using npm ci when applicable.

Some unscientific tests from running on my mac:

Bootstrapping after git clone (no lockfiles)

⑂ next$ time yarn
8.12s user 11.56s system 127% cpu 15.458 total

⑂ lerna-use-npm$ time npm i
33.79s user 18.62s system 201% cpu 26.017 total

⑂ next$ time yarn run bootstrap
174.65s user 272.09s system 170% cpu 4:21.27 total

⑂ lerna-use-npm$ time npm run bootstrap
75.83s user 56.97s system 209% cpu 1:03.49 total

Cleaning

⑂ next$ time yarn run clean
54.27s user 510.33s system 569% cpu 1:39.17 total

⑂ lerna-use-npm$ time npm run clean
18.45s user 5.35s system 325% cpu 7.310 total

(note: this reduction is largely due to dependencies being hoisted to root node_modules)

⑂ next$ time rm -Rf node_modules
0.05s user 1.88s system 99% cpu 1.942 total

⑂ lerna-use-npm$ time rm -Rf node_modules
0.18s user 8.33s system 94% cpu 8.993 total

After repo has been cleaned

⑂ next$ time yarn
5.82s user 11.60s system 236% cpu 7.381 total

⑂ lerna-use-npm$ time npm i
25.51s user 26.28s system 167% cpu 30.946 total

⑂ lerna-use-npm$ time npm ci
7.34s user 13.22s system 240% cpu 8.538 total

(npm ci can safely be run when there's a lockfile)

⑂ next$ time yarn run bootstrap
175.29s user 271.84s system 172% cpu 4:19.28 total

⑂ lerna-use-npm$ time npm run bootstrap
73.41s user 54.27s system 206% cpu 1:01.71 total

Bootstrap after add new dependency in a package

⑂ next$ time yarn run bootstrap
7.98s user 1.81s system 55% cpu 17.635 total

⑂ lerna-use-npm$ time npm run bootstrap
30.25s user 3.29s system 100% cpu 33.305 total

[rexxars]

👍