Add new PBR Neutral tone mapper (#7597)

This tone mapper was designed to preserve the color apperance
of materials. It provides good saturation and contrast while
controlling the highlights.

android/filament-android/src/main/cpp/ToneMapper.cpp

@@ -47,6 +47,11 @@ Java_com_google_android_filament_ToneMapper_nCreateFilmicToneMapper(JNIEnv*, jcl
     return (jlong) new FilmicToneMapper();
 }
 
+extern "C" JNIEXPORT jlong JNICALL
+Java_com_google_android_filament_ToneMapper_nCreatePBRNeutralToneMapper(JNIEnv*, jclass) {
+    return (jlong) new PBRNeutralToneMapper();
+}
+
 extern "C" JNIEXPORT jlong JNICALL
 Java_com_google_android_filament_ToneMapper_nCreateAgxToneMapper(JNIEnv*, jclass, jint look) {
     return (jlong) new AgxToneMapper(AgxToneMapper::AgxLook(look));