Enable incompatible_disallow_load_labels_to_cross_package_boundaries by default

Fixes https://github.com/bazelbuild/bazel/issues/6408

Tested: https://buildkite.com/bazel/bazelisk-plus-incompatible-flags/builds/52

RELNOTES: `--incompatible_disallow_load_labels_to_cross_package_boundaries` is enabled by default
PiperOrigin-RevId: 240347889

src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java

diff --git a/src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java b/src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java
index 095e3e83..59b6376 100644
--- a/src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java
+++ b/src/main/java/com/google/devtools/build/lib/packages/StarlarkSemanticsOptions.java
@@ -313,7 +313,7 @@
 
   @Option(
       name = "incompatible_disallow_load_labels_to_cross_package_boundaries",
-      defaultValue = "false",
+      defaultValue = "true",
       documentationCategory = OptionDocumentationCategory.STARLARK_SEMANTICS,
       effectTags = {OptionEffectTag.BUILD_FILE_SEMANTICS},
       metadataTags = {

src/main/java/com/google/devtools/build/lib/skyframe/SkylarkModuleCycleReporter.java

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/SkylarkModuleCycleReporter.java b/src/main/java/com/google/devtools/build/lib/skyframe/SkylarkModuleCycleReporter.java
index 71035b4..12ab5e0 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/SkylarkModuleCycleReporter.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/SkylarkModuleCycleReporter.java
@@ -127,11 +127,10 @@
                     + "' was defined too late in your WORKSPACE file."));
         return true;
       } else if (Iterables.any(cycle, IS_PACKAGE_LOOKUP)) {
-        eventHandler.handle(
-            Event.error(null, "cycle detected loading "
-                + String.join(
-                    " ", lastPathElement.functionName().toString().toLowerCase().split("_"))
-                + " '" + lastPathElement.argument().toString() + "'"));
+        PackageIdentifier pkg =
+            (PackageIdentifier)
+                Iterables.getLast(Iterables.filter(cycle, IS_PACKAGE_LOOKUP)).argument();
+        eventHandler.handle(Event.error(null, "cannot load package '" + pkg + "'"));
         return true;
       }
     }

src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java

diff --git a/src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java b/src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java
index 9e54d4c..c60216d 100644
--- a/src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java
+++ b/src/main/java/com/google/devtools/build/lib/syntax/StarlarkSemantics.java
@@ -219,7 +219,7 @@
           .incompatibleDisallowFileType(true)
           .incompatibleDisallowLegacyJavaProvider(false)
           .incompatibleDisallowLegacyJavaInfo(false)
-          .incompatibleDisallowLoadLabelsToCrossPackageBoundaries(false)
+          .incompatibleDisallowLoadLabelsToCrossPackageBoundaries(true)
           .incompatibleDisallowNativeInBuildFile(false)
           .incompatibleDisallowOldStyleArgsAdd(true)
           .incompatibleDisallowStructProviderSyntax(false)