[JS IR BE] Preserve package fqName when moving external declarations out

Create separate package fragment for each fqName of external declaration package

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/JsIrBackendContext.kt

@@ -55,7 +55,7 @@ class JsIrBackendContext(
 
     override var inVerbosePhase: Boolean = false
 
-    lateinit var externalPackageFragment: IrPackageFragment
+    var externalPackageFragment = mutableMapOf<FqName, IrPackageFragment>()
     lateinit var bodilessBuiltInsPackageFragment: IrPackageFragment
 
     val externalNestedClasses = mutableListOf<IrClass>()

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/lower/MoveBodilessDeclarationsToSeparatePlace.kt

@@ -55,12 +55,6 @@ private class DescriptorlessExternalPackageFragmentSymbol : IrExternalPackageFra
 }
 
 fun moveBodilessDeclarationsToSeparatePlace(context: JsIrBackendContext, module: IrModuleFragment) {
-    val externalPackageFragment = IrExternalPackageFragmentImpl(
-        DescriptorlessExternalPackageFragmentSymbol(),
-        FqName.ROOT
-    )
-
-    context.externalPackageFragment = externalPackageFragment
 
     val bodilessBuiltInsPackageFragment = IrExternalPackageFragmentImpl(
         DescriptorlessExternalPackageFragmentSymbol(),
@@ -86,6 +80,15 @@ fun moveBodilessDeclarationsToSeparatePlace(context: JsIrBackendContext, module:
     }
 
     fun lowerFile(irFile: IrFile): IrFile? {
+        val externalPackageFragment by lazy {
+            context.externalPackageFragment.getOrPut(irFile.fqName) {
+                IrExternalPackageFragmentImpl(
+                    DescriptorlessExternalPackageFragmentSymbol(),
+                    irFile.fqName
+                )
+            }
+        }
+
         context.externalNestedClasses += collectExternalClasses(irFile, includeCurrentLevel = false)
 
         if (irFile.getJsModule() != null || irFile.getJsQualifier() != null) {

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/transformers/irToJs/IrModuleToJsTransformer.kt

@@ -121,8 +121,7 @@ class IrModuleToJsTransformer(
 
     private fun generateModule(module: IrModuleFragment): JsProgram {
         val additionalPackages = with(backendContext) {
-            listOf(
-                externalPackageFragment,
+            externalPackageFragment.values + listOf(
                 bodilessBuiltInsPackageFragment,
                 intrinsics.externalPackageFragment
             ) + packageLevelJsModules