[JS] Keep interfaces

^KT-54173 fixed

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/JsUsefulDeclarationProcessor.kt

@@ -127,7 +127,8 @@ internal class JsUsefulDeclarationProcessor(
 
     override fun processSuperTypes(irClass: IrClass) {
         irClass.superTypes.forEach {
-            if (!it.isInterface()) {
+            val shouldClassBeKept = it.classOrNull?.let { context.keeper.shouldKeep(it.owner) } ?: false
+            if (!it.isInterface() || shouldClassBeKept) {
                 (it.classifierOrNull as? IrClassSymbol)?.owner?.enqueue(irClass, "superTypes")
             }
         }

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/dce/UselessDeclarationsRemover.kt

@@ -63,7 +63,7 @@ class UselessDeclarationsRemover(
 
     private fun IrClassSymbol.collectUsedSuperTypes(): Set<IrClassSymbol> {
         return savedTypesCache.getOrPut(this) {
-            if (owner in usefulDeclarations) {
+            if (owner in usefulDeclarations || context.keeper.shouldKeep(owner)) {
                 setOf(this)
             } else {
                 owner.superTypes