Do not force loading all kt-files inside LazyPackageDescriptor constructor

Effectively it leads to all stubs being built for any once used package

The idea is that they only were used for FILE_TO_PACKAGE_FRAGMENT
that is mostly read in backend and rarely in the IDE, so we can replace
its usages with searching through related package-fragments

compiler/backend/src/org/jetbrains/kotlin/codegen/MultifileClassCodegen.kt

@@ -41,6 +41,7 @@ import org.jetbrains.kotlin.resolve.jvm.diagnostics.MultifileClass
 import org.jetbrains.kotlin.resolve.jvm.diagnostics.MultifileClassPart
 import org.jetbrains.kotlin.resolve.jvm.diagnostics.OtherOrigin
 import org.jetbrains.kotlin.resolve.jvm.jvmSignature.JvmMethodSignature
+import org.jetbrains.kotlin.resolve.lazy.descriptors.findPackageFragmentForFile
 import org.jetbrains.kotlin.resolve.scopes.DescriptorKindFilter
 import org.jetbrains.kotlin.resolve.scopes.MemberScope
 import org.jetbrains.kotlin.serialization.deserialization.descriptors.DeserializedCallableMemberDescriptor
@@ -63,7 +64,7 @@ class MultifileClassCodegenImpl(
 ) : MultifileClassCodegen {
     private val facadeClassType = AsmUtil.asmTypeByFqNameWithoutInnerClasses(facadeFqName)
 
-    private val packageFragment = getOnlyPackageFragment(facadeFqName.parent(), files, state.bindingContext)
+    private val packageFragment = getOnlyPackageFragment(facadeFqName.parent(), files, state.module)
 
     private val compiledPackageFragment = getCompiledPackageFragment(facadeFqName, state)
 
@@ -352,10 +353,10 @@ class MultifileClassCodegenImpl(
         private val J_L_OBJECT = AsmTypes.OBJECT_TYPE.internalName
         private val FACADE_CLASS_ATTRIBUTES = Opcodes.ACC_PUBLIC or Opcodes.ACC_FINAL or Opcodes.ACC_SUPER
 
-        private fun getOnlyPackageFragment(packageFqName: FqName, files: Collection<KtFile>, bindingContext: BindingContext): PackageFragmentDescriptor? {
+        private fun getOnlyPackageFragment(packageFqName: FqName, files: Collection<KtFile>, moduleDescriptor: ModuleDescriptor): PackageFragmentDescriptor? {
             val fragments = SmartList<PackageFragmentDescriptor>()
             for (file in files) {
-                val fragment = bindingContext.get(BindingContext.FILE_TO_PACKAGE_FRAGMENT, file)
+                val fragment = moduleDescriptor.findPackageFragmentForFile(file)
                                ?: throw AssertionError("package fragment is null for " + file + "\n" + file.text)
 
                 assert(packageFqName == fragment.fqName) { "expected package fq name: " + packageFqName + ", actual: " + fragment.fqName }

compiler/backend/src/org/jetbrains/kotlin/codegen/PackageCodegenImpl.java

@@ -32,8 +32,8 @@ import org.jetbrains.kotlin.fileClasses.JvmFileClassUtil;
 import org.jetbrains.kotlin.name.FqName;
 import org.jetbrains.kotlin.progress.ProgressIndicatorAndCompilationCanceledStatus;
 import org.jetbrains.kotlin.psi.*;
-import org.jetbrains.kotlin.resolve.BindingContext;
 import org.jetbrains.kotlin.resolve.jvm.diagnostics.JvmDeclarationOriginKt;
+import org.jetbrains.kotlin.resolve.lazy.descriptors.PackageDescriptorUtilKt;
 import org.jetbrains.org.objectweb.asm.Type;
 
 import java.util.ArrayList;
@@ -131,7 +131,8 @@ public class PackageCodegenImpl implements PackageCodegen {
     private PackageFragmentDescriptor getOnlyPackageFragment(@NotNull FqName expectedPackageFqName) {
         SmartList<PackageFragmentDescriptor> fragments = new SmartList<>();
         for (KtFile file : files) {
-            PackageFragmentDescriptor fragment = state.getBindingContext().get(BindingContext.FILE_TO_PACKAGE_FRAGMENT, file);
+            PackageFragmentDescriptor fragment =
+                    PackageDescriptorUtilKt.findPackageFragmentForFile(state.getModule(), file);
             assert fragment != null : "package fragment is null for " + file + "\n" + file.getText();
 
             assert expectedPackageFqName.equals(fragment.getFqName()) :