FIR. Refactor smart-cast representation in FIR tree

Make smart-casts non-transparent expression without delegation
to underlying FirQualifiedAccessExpression, as children delegation in
fir tree has unclear semantics
Remove two different kinds of tree nodes for smart-casts

compiler/tests-common-new/tests-gen/org/jetbrains/kotlin/test/runners/ir/IrTextTestGenerated.java

@@ -2596,12 +2596,6 @@ public class IrTextTestGenerated extends AbstractIrTextTest {
             runTest("compiler/testData/ir/irText/firProblems/InnerClassInAnonymous.kt");
         }
 
-        @Test
-        @TestMetadata("JCTree.kt")
-        public void testJCTree() throws Exception {
-            runTest("compiler/testData/ir/irText/firProblems/JCTree.kt");
-        }
-
         @Test
         @TestMetadata("kt19251.kt")
         public void testKt19251() throws Exception {
@@ -2638,6 +2632,12 @@ public class IrTextTestGenerated extends AbstractIrTextTest {
             runTest("compiler/testData/ir/irText/firProblems/MultiList.kt");
         }
 
+        @Test
+        @TestMetadata("OutBox.kt")
+        public void testOutBox() throws Exception {
+            runTest("compiler/testData/ir/irText/firProblems/OutBox.kt");
+        }
+
         @Test
         @TestMetadata("putIfAbsent.kt")
         public void testPutIfAbsent() throws Exception {

compiler/tests-common-new/tests/org/jetbrains/kotlin/test/frontend/fir/handlers/FirDiagnosticsHandler.kt

@@ -54,6 +54,7 @@ class FirDiagnosticsHandler(testServices: TestServices) : FirAnalysisHandler(tes
             KtRealSourceElementKind,
             KtFakeSourceElementKind.DesugaredCompoundAssignment,
             KtFakeSourceElementKind.ReferenceInAtomicQualifiedAccess,
+            KtFakeSourceElementKind.SmartCastExpression
         )
     }
 
@@ -158,7 +159,7 @@ class FirDiagnosticsHandler(testServices: TestServices) : FirAnalysisHandler(tes
                         )
                     )
                 }
-                if (element is FirExpressionWithSmartcast) {
+                if (element is FirSmartCastExpression) {
                     element.originalExpression.acceptChildren(this)
                 } else {
                     element.acceptChildren(this)
@@ -205,7 +206,7 @@ class FirDiagnosticsHandler(testServices: TestServices) : FirAnalysisHandler(tes
         diagnosedRangesToDiagnosticNames: Map<IntRange, Set<String>>
     ): KtDiagnosticWithParameters1<String>? =
         DebugInfoDiagnosticFactory1.EXPRESSION_TYPE.createDebugInfoDiagnostic(element, diagnosedRangesToDiagnosticNames) {
-            element.typeRef.renderAsString((element as? FirExpressionWithSmartcast)?.takeIf { it.isStable }?.originalType)
+            element.typeRef.renderAsString((element as? FirSmartCastExpression)?.takeIf { it.isStable }?.originalExpression?.typeRef)
         }
 
     private fun FirTypeRef.renderAsString(originalTypeRef: FirTypeRef?): String {