Previously, we would archive every file in node_modules, however we
only actually needed the production modules. This change adds an
implicit ignorer when walking a directory that has a package.json file
in to exclude stuff under `node_modules` which is not pulled in via an
entry in the `dependencies` section of the package.json.
This change will also cause the archives that we upload to not include
either pulumi or any @pulumi/... packages, since they are not listed
in the dependencies section ofa package.json. This is fine, since we
linked in the versions we have in the cloud anyway. When we move to
using npm for these packages (instead of linking) then they will be
included.