feat: raise config action issue if failing to look up locked dependency (#1704)

If an npm dependency can’t be found, and the package.json has a lock file, then Renovate will encounter lock file errors every time *any* dependency in that package.json has an update. Instead of raising PRs with an error, we instead now stop raising PRs and instead raise a config warning issue. Users can “dismiss” this by setting config option `updateLockFiles` to false.

Closes #1697