Use instance methods instead of JetPsiUtil for getting fq names

Remove unnecessary usages of JetFile#getPackageDirective where only FqName is needed
Make JetFile#getPackageFqName not nullable to avoid confusion on call sites
Remove getPackageName usages
Move getFqName(JetNamedDeclaration) to a separate util class

compiler/jet.as.java.psi/src/org/jetbrains/jet/asJava/KotlinJavaFileStubProvider.java

@@ -181,7 +181,7 @@ public class KotlinJavaFileStubProvider<T extends WithFileStub> implements Cache
                     @NotNull
                     @Override
                     public FqName getPackageFqName() {
-                        return JetPsiUtil.getFQName(getFile());
+                        return getFile().getPackageFqName();
                     }
 
                     @Override

compiler/jet.as.java.psi/src/org/jetbrains/jet/asJava/KotlinLightClassForExplicitDeclaration.java

@@ -288,7 +288,7 @@ public class KotlinLightClassForExplicitDeclaration extends KotlinWrappingLightC
                 @NotNull
                 @Override
                 public String getPackageName() {
-                    return JetPsiUtil.getFQName((JetFile) classOrObject.getContainingFile()).asString();
+                    return ((JetFile) classOrObject.getContainingFile()).getPackageFqName().asString();
                 }
 
                 @NotNull

compiler/jet.as.java.psi/src/org/jetbrains/jet/asJava/LightClassUtil.java

@@ -234,12 +234,9 @@ public class LightClassUtil {
 
         if (parent instanceof JetFile) {
             // top-level declaration
-            FqName fqName = getPackageClassNameForFile((JetFile) parent);
-            if (fqName != null) {
-                Project project = declaration.getProject();
-
-                return JavaElementFinder.getInstance(project).findClass(fqName.asString(), GlobalSearchScope.allScope(project));
-            }
+            FqName fqName = PackageClassUtils.getPackageClassFqName(((JetFile) parent).getPackageFqName());
+            Project project = declaration.getProject();
+            return JavaElementFinder.getInstance(project).findClass(fqName.asString(), GlobalSearchScope.allScope(project));
         }
         else if (parent instanceof JetClassBody) {
             assert parent.getParent() instanceof JetClassOrObject;
@@ -249,12 +246,6 @@ public class LightClassUtil {
         return null;
     }
 
-    @Nullable
-    private static FqName getPackageClassNameForFile(@NotNull JetFile jetFile) {
-        String packageName = jetFile.getPackageName();
-        return packageName == null ? null : PackageClassUtils.getPackageClassFqName(new FqName(packageName));
-    }
-
     @NotNull
     private static PropertyAccessorsPsiMethods extractPropertyAccessors(
             @NotNull JetDeclaration jetDeclaration,

compiler/jet.as.java.psi/src/org/jetbrains/jet/asJava/StubClassBuilder.java

@@ -30,7 +30,6 @@ import org.jetbrains.asm4.FieldVisitor;
 import org.jetbrains.asm4.MethodVisitor;
 import org.jetbrains.jet.codegen.AbstractClassBuilder;
 import org.jetbrains.jet.lang.psi.JetFile;
-import org.jetbrains.jet.lang.psi.JetPsiUtil;
 import org.jetbrains.jet.lang.resolve.java.PackageClassUtils;
 import org.jetbrains.jet.lang.resolve.name.FqName;
 
@@ -81,7 +80,7 @@ public class StubClassBuilder extends AbstractClassBuilder {
         super.defineClass(origin, version, access, name, signature, superName, interfaces);
 
         if (origin instanceof JetFile) {
-            FqName packageName = JetPsiUtil.getFQName((JetFile) origin);
+            FqName packageName = ((JetFile) origin).getPackageFqName();
             String packageClassName = PackageClassUtils.getPackageClassName(packageName);
 
             if (name.equals(packageClassName) || name.endsWith("/" + packageClassName)) {