[K2]: Support java-kotlin interop for @SubclassOptInRequired

Previously, if the parent class was in Java code and the subclass in
Kotlin, the opt-in usage error would not be reported for the subclass.
The problem was that the extractClassFromArgument function couldn't get
the class type from Java code. It was looking for a ConeClassLikeType,
but found a ConeFlexibleType instead.

#KT-60258 Fixed

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/JavaKotlinInterop.fir.kt

@@ -0,0 +1,13 @@
+// FILE: one.java
+package pcg;
+
+import kotlin.ExperimentalMultiplatform;
+import kotlin.SubclassOptInRequired;
+@SubclassOptInRequired(markerClass = ExperimentalMultiplatform.class) public class Foo{}
+
+// FILE: two.kt
+
+import pcg.Foo
+
+class Bar() : <!OPT_IN_USAGE_ERROR!>Foo<!>()
+

compiler/testData/diagnostics/testsWithStdLib/annotations/subclassOptInRequired/JavaKotlinInterop.kt

@@ -0,0 +1,14 @@
+// FILE: one.java
+package pcg;
+
+import kotlin.ExperimentalMultiplatform;
+import kotlin.SubclassOptInRequired;
+@SubclassOptInRequired(markerClass = ExperimentalMultiplatform.class) public class Foo{}
+
+// FILE: two.kt
+
+import pcg.Foo
+
+class Bar() : Foo()
+
+