This change ensures an fsync after updating `package.json` on Windows,
which prevents an issue that intermittently occurs when rolling back a
package with many dependencies such as fsevents.

In testing it does not appear that fsync has as much of a performance
impact on Windows as it does on other platforms, so this should not affect
install times on Windows materially.

Fixes: #17671
Fixes: #18287
Fixes: #18453
Fixes: #18380
Fixes: #18441
PR-URL: npm/npm#18458
Credit: @marcins
Reviewed-By: @iarna

Now that we have a refresh-package-json phase, full package data is not
available in the move phase, so writing here deletes important info.  Beyond
that, the `refresh-package-json` phase takes care of the writing for us.

Use fetchPackageMetadata to get metadata for extracting version from
packages instead of cache.add (which in npm5 does not actually return
package metadata anymore)

PR-URL: npm/npm#18385
Fixes: #16825
Credit: @joshclow
Reviewed-By: @iarna

The "notice" loglevel was added and made the default in `npm@5`, but the
docs were not updated to this change. This patch updates the loglevel
docs to the new default and adds "notice" to the list of possible
values.

I don't know how to describe "notice" so I just left it at that.

PR-URL: npm/npm#18397
Credit: @kenany
Reviewed-By: @iarna

PR-URL: npm/npm#18372
Credit: @jakubholynet
Reviewed-By: @iarna