[FIR-TEST] Add new testdata generated after changes in previous commit

compiler/testData/diagnostics/tests/IsExpressions.fir.kt

@@ -0,0 +1,26 @@
+// FILE: KotlinFile.kt
+
+fun test() {
+   if (1 is Int) {
+     if (1 is Boolean) {
+
+     }
+   }
+
+   A.create() is A
+   A.create() is A?
+
+   <!UNRESOLVED_REFERENCE!>unresolved<!> is A
+   <!UNRESOLVED_REFERENCE!>unresolved<!> is A?
+
+   val x = foo()
+   x as String
+   x is String
+}
+
+fun foo(): Any = ""
+
+// FILE: A.java
+class A {
+    static A create() { return null; }
+}