[FIR] fix subtyping for definitely notnull types.

The current implementation doesn't consider Foo a subtype of Captured<in
Foo>!!, since AbstractTypeCheckerContext::checkSubtypeForSpecialCases
does not handle DefinitelyNotNullType cases. This PR adds handling of
DefinitelyNotNullType by looking at its original type.

^KT-42824 Fixed

compiler/testData/codegen/box/javaInterop/generics/kt42824.kt

@@ -0,0 +1,21 @@
+// FILE: DiagnosticFactory0.java
+
+import org.jetbrains.annotations.NotNull;
+
+public class DiagnosticFactory0<E> {
+    @NotNull
+    public SimpleDiagnostic<E> on(@NotNull E element) {
+        return new SimpleDiagnostic<>(element);
+    }
+}
+
+// FILE: test.kt
+
+class SimpleDiagnostic<E>(val element: E)
+interface KtAnnotationEntry
+
+fun foo(error: DiagnosticFactory0<in KtAnnotationEntry>, entry: KtAnnotationEntry) {
+    error.on(entry) // used to be INAPPLICABLE_CANDIDATE
+}
+
+fun box() = "OK"