[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/labels/qualifiedThisInExtensionProperty.fir.kt

@@ -0,0 +1,15 @@
+// WITH_STDLIB
+// ISSUE: KT-20617
+
+fun Int.function() = run {
+    this@function + 1
+}
+
+val Int.property1: Int
+    get() {
+        return run { this@property1 + 1 }
+    }
+
+val Int.property2 get() = run {
+    this@property2 + 1
+}

compiler/testData/diagnostics/tests/labels/qualifiedThisInExtensionProperty.kt

@@ -0,0 +1,15 @@
+// WITH_STDLIB
+// ISSUE: KT-20617
+
+fun Int.function() = run {
+    this@function + 1
+}
+
+val Int.property1: Int
+    get() {
+        return run { this@property1 + 1 }
+    }
+
+val Int.property2 get() = run {
+    this<!UNRESOLVED_REFERENCE!>@property2<!> <!DEBUG_INFO_MISSING_UNRESOLVED!>+<!> 1
+}