IR: don't use descriptors in rendering (work in progress)

There's some descriptor-based code remaining. Need some more work on IR.

compiler/testData/ir/irText/expressions/whenElse.txt

@@ -1,9 +1,8 @@
 FILE fqName:<root> fileName:/whenElse.kt
-  FUN name:test visibility:public modality:FINAL <> () returnType:kotlin.Int flags:
+  FUN name:test visibility:public modality:FINAL <> () returnType:kotlin.Int flags:[]
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='test(): Int'
+      RETURN type=kotlin.Nothing from='FUN name:test visibility:public modality:FINAL <> () returnType:kotlin.Int flags:[]'
         WHEN type=kotlin.Int origin=WHEN
           BRANCH
             if: CONST Boolean type=kotlin.Boolean value=true
             then: CONST Int type=kotlin.Int value=42
-