FIR: Fix bare type case with flexible supertypes

compiler/fir/analysis-tests/testData/resolve/types/bareWithFlexibleArg.fir.txt

@@ -0,0 +1,6 @@
+FILE: main.kt
+    public final fun foo(x: R|Promise<kotlin/String?>|): R|kotlin/Unit| {
+        R|/bar|((R|<local>/x| as R|CancellablePromise<kotlin/String?>|))
+    }
+    public final fun bar(x: R|CancellablePromise<kotlin/String?>|): R|kotlin/Unit| {
+    }

compiler/fir/analysis-tests/testData/resolve/types/bareWithFlexibleArg.kt

@@ -0,0 +1,15 @@
+// FIR_IDENTICAL
+// SKIP_TXT
+
+// FILE: Promise.java
+public interface Promise<T> {}
+
+// FILE: CancellablePromise.java
+public interface CancellablePromise<E> extends Promise<E> {}
+
+// FILE: main.kt
+fun foo(x: Promise<String?>) {
+    bar(x as CancellablePromise)
+}
+fun bar(x: CancellablePromise<String?>) {}
+