Do preparation of enhancement as well (for types with enhancement), during subtype checks

^KT-47899 Fixed

compiler/testData/diagnostics/foreignAnnotationsTests/java8Tests/jspecify/warnMode/kt47899.kt

@@ -0,0 +1,15 @@
+// JSPECIFY_STATE: warn
+
+// FILE: Foo.java
+import org.jspecify.nullness.Nullable;
+
+public class Foo {
+    public static <T> void gauge(@Nullable T stateObject) {}
+}
+
+// FILE: main.kt
+fun <T> test(metric: T) {
+    if (metric is String) {
+        Foo.gauge(<!DEBUG_INFO_SMARTCAST!>metric<!>)
+    }
+}