[FIR] Do not smartcast class delegation implemented properties

When a property is implemented via class delegation, it should be
considered unstable for smart-casting. This is because it is unknown
what kind of stability the underlying class delegate property has. It
could be a stable property, or it could be implemented via a custom
getter and unstable.

^KT-57417 Fixed

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirLightTreeOldFrontendDiagnosticsTestGenerated.java

@@ -34635,6 +34635,12 @@ public class FirLightTreeOldFrontendDiagnosticsTestGenerated extends AbstractFir
                     runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/capturedInlineModifiedBefore.kt");
                 }
 
+                @Test
+                @TestMetadata("classDelegation.kt")
+                public void testClassDelegation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/classDelegation.kt");
+                }
+
                 @Test
                 @TestMetadata("doWhileWithBreak.kt")
                 public void testDoWhileWithBreak() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirPsiOldFrontendDiagnosticsTestGenerated.java

@@ -34761,6 +34761,12 @@ public class FirPsiOldFrontendDiagnosticsTestGenerated extends AbstractFirPsiDia
                     runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/capturedInlineModifiedBefore.kt");
                 }
 
+                @Test
+                @TestMetadata("classDelegation.kt")
+                public void testClassDelegation() throws Exception {
+                    runTest("compiler/testData/diagnostics/tests/smartCasts/varnotnull/classDelegation.kt");
+                }
+
                 @Test
                 @TestMetadata("doWhileWithBreak.kt")
                 public void testDoWhileWithBreak() throws Exception {