Create ValidationEnvironment from Environment

Allow ValidationEnvironment to be created from initial Environment so that
there is no need to manually keep two different sets of constructors in synch.

--
MOS_MIGRATED_REVID=101588695
diff --git a/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredRuleClassProvider.java b/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredRuleClassProvider.java
index 543c71e..40253e5 100644
--- a/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredRuleClassProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/analysis/ConfiguredRuleClassProvider.java
@@ -229,7 +229,7 @@
    * Used to make the label instances unique, so that we don't create a new
    * instance for every rule.
    */
-  private static LoadingCache<String, Label> LABELS = CacheBuilder.newBuilder().build(
+  private static final LoadingCache<String, Label> LABELS = CacheBuilder.newBuilder().build(
       new CacheLoader<String, Label>() {
     @Override
     public Label load(String from) {
@@ -307,8 +307,9 @@
     this.configurationCollectionFactory = configurationCollectionFactory;
     this.prerequisiteValidator = prerequisiteValidator;
     this.skylarkAccessibleJavaClasses = skylarkAccessibleJavaClasses;
-    this.skylarkValidationEnvironment = SkylarkModules.getValidationEnvironment(
-        skylarkAccessibleJavaClasses.keySet());
+    this.skylarkValidationEnvironment = new ValidationEnvironment(
+        // TODO(bazel-team): refactor constructors so we don't have those null-s
+        createSkylarkRuleClassEnvironment(null, null));
   }
 
   public PrerequisiteValidator getPrerequisiteValidator() {