Package access implements a config service access check against a project config client.
Note that this is a soft check, as the true access authority is the config service, and this check is not hitting that service.
If access is granted, this function will return nil. If access is explicitly denied, this will return ErrNoAccess.
This is a port of the ACL implementation from the config service: https://chromium.googlesource.com/external/github.com/luci/luci-py/+/e3fbb1f5dafa59a2c57cf3a9fe3708f4309ab653/appengine/components/components/config/api.py
ErrNoAccess is an error returned by CheckAccess if the supplied Authority does not have access to the supplied config set.
Check tests if a given Authority can access the named config set.