Solve the constraint system for alpha-converted variables,

store initial and backward conversions for
substituting new constraints and the result

compiler/testData/diagnostics/tests/inference/constraints/kt6320.kt

@@ -15,6 +15,6 @@ class C<X, Z, Y : X>
 
 class D<X, Z, Y : X>(<!UNUSED_PARAMETER!>foo<!>: C<X, Z, Y>) {
     fun test(a: C<Y, Y, Y>) {
-        val d: D<X, Y, Y> = <!TYPE_MISMATCH!>D(a)<!>
+        val d: D<X, Y, Y> = <!TYPE_INFERENCE_EXPECTED_TYPE_MISMATCH!>D<!>(a)
     }
 }

compiler/testData/diagnostics/tests/inference/constraints/notNullConstraintOnNullableType.kt

@@ -17,8 +17,8 @@ fun test(out: Out<Int>, i: In<Int>, inv: A<Int>) {
     r checkType { _<Int>() }
 
     // T? <: Int => error
-    doIn(<!TYPE_MISMATCH!>i<!>)
+    <!TYPE_INFERENCE_INCORPORATION_ERROR!>doIn<!>(<!TYPE_MISMATCH!>i<!>)
 
     // T? >: Int => error
-    doA(<!TYPE_MISMATCH!>inv<!>)
+    <!TYPE_INFERENCE_INCORPORATION_ERROR!>doA<!>(<!TYPE_MISMATCH!>inv<!>)
 }