Prefactoring for making "blaze test <alias target>" work.

Mainly renaming classes and variables and shuffling things around so that the actual functional change is as small as possible.

RELNOTES: None.
PiperOrigin-RevId: 281043194
diff --git a/src/main/java/com/google/devtools/build/lib/packages/TargetUtils.java b/src/main/java/com/google/devtools/build/lib/packages/TargetUtils.java
index e22434d..156d08e 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/TargetUtils.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/TargetUtils.java
@@ -82,6 +82,16 @@
     return target instanceof Rule && isTestSuiteRuleName(((Rule) target).getRuleClass());
   }
 
+  /** Returns true iff {@code target} is an {@code alias} rule. */
+  public static boolean isAlias(Target target) {
+    if (!(target instanceof Rule)) {
+      return false;
+    }
+
+    Rule rule = (Rule) target;
+    return !rule.getRuleClassObject().isSkylark() && rule.getRuleClass().equals("alias");
+  }
+
   /**
    * Returns true iff {@code target} is a {@code *_test} or {@code test_suite}.
    */