Consolidate File.Rules() and RulesAt() (#1091)
Consolidate File.Rules() and RulesAt() (#1091)

and allow RulesAt to find targets nested in list comprehensions,
matching the behaviour added to Rules() in
82b21607e00913b16fe1c51bec80232d9d6de31c.
bazelbuild/buildtools,bazelbuild/buildtools,bazelbuild/buildtools,bazelbuild/buildtools,bazelbuild/buildtools