[NI] Make constraint check for type variables with complex dependency

Additional check for trivial constraints is needed to make lambda
analysis before outer variable fixation to Nothing(?)

^KT-37627 Fixed

compiler/testData/diagnostics/testsWithStdLib/inference/kt37627.kt

@@ -0,0 +1,9 @@
+// FIR_IDENTICAL
+// !LANGUAGE: +NewInference
+// !DIAGNOSTICS: -NAME_SHADOWING -UNUSED_VARIABLE
+
+fun foo(x: Int) {
+    val x = if (true) { // OI: Map<String, () → Int>?, NI: Nothing?, error
+        "" to { x }
+    } else { null }
+}

compiler/testData/diagnostics/testsWithStdLib/inference/kt37627.txt

@@ -0,0 +1,3 @@
+package
+
+public fun foo(/*0*/ x: kotlin.Int): kotlin.Unit