Tests: fix stdlib declarations in IR interpreter test data

Fix some unresolved supertypes. This is necessary to be able to enable
IR fake override builder by default (KT-61514), because it traverses all
supertypes and asserts that they're classes, so that it can build fake
overrides for declarations from there. Without this change, for example
`IrFakeOverrideBuilder.buildFakeOverridesForClass` would crash.

compiler/testData/ir/interpreter/helpers/Sets.kt

@@ -3,7 +3,7 @@
 
 package kotlin.collections
 
-internal object EmptySet : Set<Nothing>, Serializable {
+internal object EmptySet : Set<Nothing>, java.io.Serializable {
     private const val serialVersionUID: Long = 3406603774387020532
 
     override fun equals(other: Any?): Boolean = other is Set<*> && other.isEmpty()