[TEST] Migrate AbstractDiagnosticsWithExplicitApi to new test runners

compiler/testData/diagnostics/tests/testsWithExplicitApi/companionObject.kt

@@ -0,0 +1,20 @@
+// SKIP_TXT
+
+public class Bar {
+    <!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>companion object<!> {}
+}
+
+public class Bar2 {
+    <!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>companion object MyCompanion<!> {}
+}
+
+public class Bar3 {
+    /**
+     * Nested object KDoc
+     */
+    <!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>object NestedObject<!> {}
+}
+
+<!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>data class FooData2<!>(val i: Int, val s: String) {
+    <!NO_EXPLICIT_VISIBILITY_IN_API_MODE!>object NestedObject<!> {}
+}