K2: Emulate K1 behavior in case of when-elvis combination

^KT-55692 Related

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

@@ -0,0 +1,19 @@
+// FIR_IDENTICAL
+// SKIP_TXT
+
+fun <X> select(vararg x: X): X = x[0]
+fun <E> myOut(): Out<E> = TODO()
+
+interface Out<out T>
+
+fun foo(x: Int, o: Out<String>, oNullable: Out<String>?) {
+    val y: Out<*> = when {
+        x > 0 -> when {
+            x == 1 -> o
+            // Once elvis is being analyzed with expected type Out<*>, because of the @Exact annotation it sticks to that type
+            // While here, it's better to use the Out<String> type from the main branch
+            else -> oNullable ?: myOut()
+        }
+        else -> myOut<Any?>()
+    }
+}