[NI] Make subtyping algorithm more robust to error types

During subtyping/incorporation we transform types (e.g. changing nullability,
 form of the type) and, basically, we're doing this to some FIXPOINT.
 It's important that we use `KotlinType.hashCode()` to compare types, but
 for error types hashCode is a hashCode of its supertype and, for example,
 `makeNullableAsSpecified` method recreate type every time. So, we continue
 to generate new constraints and we'll never stop incorporation algorithm

compiler/testData/diagnostics/tests/cast/bare/UnrelatedColon.ni.txt

@@ -1,6 +1,6 @@
 package
 
-public fun test(/*0*/ tr: Tr): [ERROR : G]
+public fun test(/*0*/ tr: Tr): Tr
 
 public interface G</*0*/ T> {
     public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean