Fix performance regression in NI by fixing totally incorrect hashCode

The actual problem was introduced in 4f1e85b468, note how `hashCode` is implemented:
```
var currentHashCode = cachedHashCode
if (currentHashCode == 0) return currentHashCode
...
```
It's a silly bug, there should be check `if (currentHashCode != 0) ...` because `0` is used a marker for "uncomputed value".

Now, in the commit 0219b86d06 I added map with `KotlinType` as a key and because of constant `hash` for `KotlinType`, we basically got `List` instead of `Map`, which caused this performance regression

 #KT-34063 Fixed

core/descriptors/src/org/jetbrains/kotlin/types/KotlinType.kt

@@ -101,7 +101,7 @@ sealed class KotlinType : Annotated, KotlinTypeMarker {
     final override fun hashCode(): Int {
         // NB: make one read to prevent race
         var currentHashCode = cachedHashCode
-        if (currentHashCode == 0) return currentHashCode
+        if (currentHashCode != 0) return currentHashCode
 
         currentHashCode = computeHashCode()