Tests: use helper function to assert compile-time and run-time type check

To cleanup warnings about useless cast or type check that is always true.

libraries/stdlib/test/testUtils.kt

@@ -1,4 +1,14 @@
 package test
 
+import kotlin.internal.NoInfer
+import kotlin.test.fail
+
 // just a static type check
-fun <T> assertStaticTypeIs(@Suppress("UNUSED_PARAMETER") value: T) {}
+fun <T> assertStaticTypeIs(@Suppress("UNUSED_PARAMETER") value: @NoInfer T) {}
+
+inline fun <reified T> assertStaticAndRuntimeTypeIs(value: @NoInfer T) {
+    @Suppress("USELESS_CAST")
+    if ((value as Any?) !is T) {
+        fail("Expected value $value to have ${T::class} type")
+    }
+}