[IR][tests] Add tests for removal-of-abstract-fun IR linkage case

^KT-50771

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

@@ -0,0 +1,7 @@
+package lib2
+
+import lib1.A
+
+class B : A() {
+    override fun foo() = 42
+}

compiler/testData/klibABI/removeAbstractFunctionFromAbstractClass/lib2/l2.kt.1

@@ -0,0 +1,5 @@
+package lib2
+
+import lib1.A
+
+class B : A()

compiler/testData/klibABI/removeAbstractFunctionFromAbstractClass/lib2/module.info

@@ -0,0 +1,6 @@
+STEP 0:
+    dependencies: stdlib, lib1
+STEP 1:
+    dependencies: stdlib, lib1
+    modifications:
+        U : l2.kt.1 -> l2.kt