Suppress K2 specific warnings in the codebase

^KT-62472

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

@@ -105,6 +105,7 @@ abstract class UsefulDeclarationProcessor(
         addReachabilityInfoIfNeeded(from, this, description, isContagiousOverridableDeclaration)
 
         if (isContagiousOverridableDeclaration) {
+            @Suppress("USELESS_CAST") // K2 warning suppression, TODO: KT-62472
             contagiousReachableDeclarations.add(this as IrOverridableDeclaration<*>)
         }
 

compiler/ir/backend.js/src/org/jetbrains/kotlin/ir/backend/js/ic/KotlinSourceFileMetadata.kt

@@ -52,6 +52,7 @@ open class KotlinSourceFileMap<out T>(files: Map<KotlinLibraryFile, Map<KotlinSo
     operator fun get(libFile: KotlinLibraryFile, sourceFile: KotlinSourceFile): T? = get(libFile)?.get(sourceFile)
 }
 
+@Suppress("DELEGATED_MEMBER_HIDES_SUPERTYPE_OVERRIDE") // K2 warning suppression, TODO: KT-62472
 class KotlinSourceFileMutableMap<T>(
     private val files: MutableMap<KotlinLibraryFile, MutableMap<KotlinSourceFile, T>> = hashMapOf()
 ) : KotlinSourceFileMap<T>(files) {