Make InsertImplicitCasts work with Descriptors and KotlinTypes again

This is a temporary change to make sure IrType infrastructure work is in
master.

It causes some of irText tests to work incorrectly (as in master).

compiler/tests/org/jetbrains/kotlin/ir/IrTextTestCaseGenerated.java

@@ -1656,6 +1656,11 @@ public class IrTextTestCaseGenerated extends AbstractIrTextTestCase {
             runTest("compiler/testData/ir/irText/types/nullabilityAssertionOnExtensionReceiver.kt");
         }
 
+        @TestMetadata("platformTypeReceiver.kt")
+        public void testPlatformTypeReceiver() throws Exception {
+            runTest("compiler/testData/ir/irText/types/platformTypeReceiver.kt");
+        }
+
         @TestMetadata("smartCastOnFieldReceiverOfGenericType.kt")
         public void testSmartCastOnFieldReceiverOfGenericType() throws Exception {
             runTest("compiler/testData/ir/irText/types/smartCastOnFieldReceiverOfGenericType.kt");