Make some native vectorization classes package private to be consistent and a minor fix

lucene/core/src/java/org/apache/lucene/internal/vectorization/VectorizationProvider.java

@@ -171,7 +171,7 @@ static VectorizationProvider lookup(boolean testMode) {
     return new DefaultVectorizationProvider();
   }
 
-  static VectorizationProvider lookup(String className) {
+  private static VectorizationProvider lookup(String className) {
     try {
       // we use method handles with lookup, so we do not need to deal with setAccessible as we
       // have private access through the lookup:

lucene/core/src/java25/org/apache/lucene/internal/vectorization/NativeVectorUtilSupport.java

@@ -50,7 +50,7 @@
  * overhead of ensuring MemorySegments are allocated off-heap before native calls.
  */
 @SuppressWarnings("restricted")
-public final class NativeVectorUtilSupport implements VectorUtilSupport {
+final class NativeVectorUtilSupport implements VectorUtilSupport {
 
   private final VectorUtilSupport delegateVectorUtilSupport;
 
@@ -259,7 +259,9 @@ private static float invokeFloatMethodHandle(MethodHandle mh, MemorySegment a, M
   private static <T> T invokeOrDelegate(MethodHandle mh, Supplier<T> delegate, Object... args) {
     if (mh != null) {
       try {
-        return (T) mh.invokeExact(args);
+        // TODO: This is slow and we should avoid dynamic invocations and improve the test coverage
+        // (https://github.com/apache/lucene/issues/15840)
+        return (T) mh.invokeWithArguments(args);
       } catch (Throwable ex) {
         throw new AssertionError("should not reach here", ex);
       }

lucene/core/src/java25/org/apache/lucene/internal/vectorization/NativeVectorizationProvider.java

@@ -26,7 +26,7 @@
 import org.apache.lucene.util.SuppressForbidden;
 
 /** Native provider returning native implementations which delegates to Panama implementation. */
-public final class NativeVectorizationProvider extends VectorizationProvider {
+final class NativeVectorizationProvider extends VectorizationProvider {
 
   private final VectorizationProvider delegateVectorUtilProvider =
       new PanamaVectorizationProvider();