Cache "Initialize" step

[tannewt]

Why isn't the initialize step cached? Pulling down code from a bunch of different repos takes a ton of time. We could cache it based on the west config and west version.

[fabiobaltieri]

Does it? The code is on github and it does s shallow fetch it should not take too long, it'd be tricky to cache correctly too because manifests can nest indefinitely so you'd need some support from west for a key... there's probably more problems, does not strike me as a great idea anyway, but you could probably cache the modules from the caller if you have a simple setup.