Implements enableOfflineMode

[arcanis]

What's the problem this PR addresses?

We didn't have a good story for people performing local development on their projects while under network-constrained environments. I'm myself working from trains from time to time, and each time it always come a point where I want to do a quick repro with one package or another, but since I don't have network it's a pain.

How did you fix it?

A new enableOfflineMode setting tells Yarn to reuse the metadata stored in the cache, even if they may be stale (a good feature reuse of the logic @paul-soporan's originally made for perf reasons!).

Checklist

• I have read the Contributing Guide.

• I have set the packages that need to be released for my changes to be effective.

• I will check that all automated PR checks pass before the PR gets reviewed.