Dependency graph builds could be slightly smarter with disambiguation

In case multiple builds match the same sha when building a dependency graph, and maestro doesn't know which is actually in use in the repo, it may be possible to do some more disambiguation based on other files:
- If there are no asset locations for one of the builds, eliminate it from contention.
- Look at other assets in the version.details file that are on the same file. If any are not ambiguous, choose that instead.