[NI] Fix extracting type variables for flexible types in in captured types

Bug was introduced in b99efb because of lack of tests.
All code in `AbstractTypeCheckerContextForConstraintSystem.extractTypeVariableForSubtype`
  related to IN projection looks suspicious and needs further investigation

compiler/testData/diagnostics/tests/inference/capturedInProjectedFlexibleType.kt

@@ -0,0 +1,16 @@
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+
+// FILE: A.java
+
+public class A<T> {
+    public A<? super T> getSuperA() { return null; }
+}
+
+// FILE: main.kt
+
+fun <T : Any> foo(x: T?, func: (T) -> T?) {}
+
+fun test(a: A<*>) {
+    foo(a) { it.superA }
+}

compiler/testData/diagnostics/tests/inference/capturedInProjectedFlexibleType.txt

@@ -0,0 +1,12 @@
+package
+
+public fun </*0*/ T : kotlin.Any> foo(/*0*/ x: T?, /*1*/ func: (T) -> T?): kotlin.Unit
+public fun test(/*0*/ a: A<*>): kotlin.Unit
+
+public open class A</*0*/ T : kotlin.Any!> {
+    public constructor A</*0*/ T : kotlin.Any!>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open fun getSuperA(): A<in T!>!
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}