[Test] Add regression tests for issues which are fixed in K2

Related issues:
KT-10879, KT-18055, KT-20617, KT-23873
KT-25668, KT-31191, KT-33108, KT-41013
KT-51827, KT-53886, KT-56624, KT-58447
KT-58458, KT-58751, KT-58814, KT-60597
KT-62806, KT-63258, KT-63444, KT-65101
KT-65408, KT-65844, KT-66186

^KT-65926 Fixed

compiler/testData/diagnostics/tests/resolve/callToProtectedOnSmartcast.fir.kt

@@ -0,0 +1,20 @@
+// ISSUE: KT-51827
+abstract class A {
+    abstract protected val a: Any?
+
+    open class Nested(override val a: String) : A() {
+        class B {
+            fun f(other: A) {
+                other.a
+                if (other is Nested) {
+                    other.a.length
+                }
+                if (other is C) {
+                    other.a
+                }
+            }
+        }
+    }
+
+    class C(override val a: String): Nested(a)
+}

compiler/testData/diagnostics/tests/resolve/callToProtectedOnSmartcast.kt

@@ -0,0 +1,20 @@
+// ISSUE: KT-51827
+abstract class A {
+    abstract protected val a: Any?
+
+    open class Nested(override val a: String) : A() {
+        class B {
+            fun f(other: A) {
+                other.a
+                if (other is Nested) {
+                    <!DEBUG_INFO_SMARTCAST!>other<!>.a.length
+                }
+                if (other is C) {
+                    <!DEBUG_INFO_SMARTCAST!>other<!>.<!INVISIBLE_MEMBER!>a<!>
+                }
+            }
+        }
+    }
+
+    class C(override val a: String): Nested(a)
+}