[IR][tests] New test: non-abstract callable member in abstract class becomes abstract

^KT-53663

compiler/testData/klibABI/nonAbstractFunctionInAbstractClassBecomesAbstract/lib2/l2.kt

@@ -0,0 +1,21 @@
+package lib2
+
+import lib1.A
+
+class B : A() {
+    override fun baz() = -42
+
+    val unlinkedFunctionUsage get() = foo() + bar()
+}
+
+class B1 : A() {
+    override fun baz() = -42
+
+    val unlinkedFunctionUsage = foo() // Expected failure on class instance initialization.
+}
+
+class B2 : A() {
+    override fun baz() = -42
+
+    val unlinkedFunctionUsage = bar() // Expected failure on class instance initialization.
+}