Clean up AllPathsFunction and get rid of getFwdDeps(Target) and getReverseDeps(Target) from the QueryEnvironment interface, since they're no longer needed by any query functions, and also WalkableGraph#get{Direct,Reverse}Deps(SkyKey).

--
MOS_MIGRATED_REVID=96361760
diff --git a/src/main/java/com/google/devtools/build/lib/query2/BlazeQueryEnvironment.java b/src/main/java/com/google/devtools/build/lib/query2/BlazeQueryEnvironment.java
index e7992f4..a5c6d1d 100644
--- a/src/main/java/com/google/devtools/build/lib/query2/BlazeQueryEnvironment.java
+++ b/src/main/java/com/google/devtools/build/lib/query2/BlazeQueryEnvironment.java
@@ -195,29 +195,19 @@
   }
 
   @Override
-  public Collection<Target> getFwdDeps(Target target) {
-    return getTargetsFromNodes(getNode(target).getSuccessors());
-  }
-
-  @Override
   public Collection<Target> getFwdDeps(Iterable<Target> targets) {
     Set<Target> result = new HashSet<>();
     for (Target target : targets) {
-      result.addAll(getFwdDeps(target));
+      result.addAll(getTargetsFromNodes(getNode(target).getSuccessors()));
     }
     return result;
   }
 
   @Override
-  public Collection<Target> getReverseDeps(Target target) {
-    return getTargetsFromNodes(getNode(target).getPredecessors());
-  }
-
-  @Override
   public Collection<Target> getReverseDeps(Iterable<Target> targets) {
     Set<Target> result = new HashSet<>();
     for (Target target : targets) {
-      result.addAll(getReverseDeps(target));
+      result.addAll(getTargetsFromNodes(getNode(target).getPredecessors()));
     }
     return result;
   }