[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/testsWithStdLib/contracts/smartcasts/smartcastOnReceiverInComplexCondition.fir.kt

@@ -0,0 +1,14 @@
+// ISSUE: KT-31191
+import kotlin.contracts.*
+
+@OptIn(ExperimentalContracts::class)
+fun Any.isString(): Boolean {
+    contract { returns(true) implies (this@isString is String) }
+    return this is String
+}
+
+fun test(x: Any?) {
+    if (x != null && x.isString()) {
+        x.length
+    }
+}

compiler/testData/diagnostics/testsWithStdLib/contracts/smartcasts/smartcastOnReceiverInComplexCondition.kt

@@ -0,0 +1,14 @@
+// ISSUE: KT-31191
+import kotlin.contracts.*
+
+@OptIn(ExperimentalContracts::class)
+fun Any.isString(): Boolean {
+    contract { returns(true) implies (this@isString is String) }
+    return this is String
+}
+
+fun test(x: Any?) {
+    if (x != null && <!DEBUG_INFO_SMARTCAST!>x<!>.isString()) {
+        x.<!UNRESOLVED_REFERENCE!>length<!>
+    }
+}