[NI] Don't skip constraints with projections during variable fixation

Those constraints are only restored for variable fixation stage because of the
influence on pefrormance.

^KT-37650 Fixed
^KT-37380 Fixed

compiler/testData/diagnostics/tests/inference/regressions/kt37650.kt

@@ -0,0 +1,14 @@
+// FIR_IDENTICAL
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE
+
+class Inv<T>
+
+fun <T> materialize(): T = TODO()
+
+fun <A> foo(x: Inv<A>) {}
+fun <B> bar(y: Inv<out B>): Inv<Inv<out B>> = materialize()
+
+fun <K> test(plant: Inv<out K>) {
+    val x = foo(bar(plant)) // OK in OI, NI: "Not enough information to infer type variable A"
+}

compiler/testData/diagnostics/tests/inference/regressions/kt37650.txt

@@ -0,0 +1,13 @@
+package
+
+public fun </*0*/ B> bar(/*0*/ y: Inv<out B>): Inv<Inv<out B>>
+public fun </*0*/ A> foo(/*0*/ x: Inv<A>): kotlin.Unit
+public fun </*0*/ T> materialize(): T
+public fun </*0*/ K> test(/*0*/ plant: Inv<out K>): kotlin.Unit
+
+public final class Inv</*0*/ T> {
+    public constructor Inv</*0*/ T>()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}