FE: add tests for KT-53966 (positive/negative)

compiler/fir/analysis-tests/testData/resolveWithStdlib/problems/falseSamConversion.kt

@@ -0,0 +1,13 @@
+// FILE: SamInterface.java
+
+public interface SamInterface {
+    public boolean foo(String arg);
+}
+
+// FILE: test.kt
+
+class Wrapper(val si: SamInterface?)
+
+fun test(w: Wrapper?) {
+    Wrapper(w?.let { it.si })
+}