[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/properties/inferenceFromGetters/recursiveGetter.kt

@@ -10,7 +10,7 @@ class A {
     val a get() = <!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>b<!>
     val b get() = <!NI;DEBUG_INFO_MISSING_UNRESOLVED, TYPECHECKER_HAS_RUN_INTO_RECURSIVE_PROBLEM!>a<!>
 
-    val z1 get() = id(<!NI;DEBUG_INFO_MISSING_UNRESOLVED, OI;DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE, TYPECHECKER_HAS_RUN_INTO_RECURSIVE_PROBLEM!>z1<!>)
+    val <!NI;IMPLICIT_NOTHING_PROPERTY_TYPE!>z1<!> get() = id(<!NI;DEBUG_INFO_MISSING_UNRESOLVED, OI;DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE, TYPECHECKER_HAS_RUN_INTO_RECURSIVE_PROBLEM!>z1<!>)
     val z2 get() = l(<!NI;DEBUG_INFO_MISSING_UNRESOLVED, OI;DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE, TYPECHECKER_HAS_RUN_INTO_RECURSIVE_PROBLEM!>z2<!>)
 
     val u get() = <!UNRESOLVED_REFERENCE!>field<!>