Support SAM conversion in psi2ir

SAM conversion takes a function value (function type or a subtype),
and produces a SAM interface value.

compiler/testData/ir/irText/expressions/sam/samConversionsWithSmartCasts.kt

@@ -0,0 +1,71 @@
+// !LANGUAGE: -NewInference
+// NB new inference doesn't really work with old JVM back-end.
+
+// WITH_JDK
+// FILE: samConversionsWithSmartCasts.kt
+
+fun test1(a: () -> Unit) {
+    if (a is Runnable) {
+        J.runStatic(a)
+    }
+}
+
+fun test2(a: () -> Unit) {
+    if (a is Runnable) {
+        J().run1(a)
+    }
+}
+
+fun test3(a: () -> Unit) {
+    if (a is Runnable) {
+        J().run2(a, a)
+    }
+}
+
+fun test4(a: () -> Unit, b: () -> Unit) {
+    if (a is Runnable) {
+        J().run2(a, b)
+    }
+}
+
+fun test5(a: Any) {
+    if (a is Runnable) {
+        J().run1(a)
+    }
+}
+
+fun test5x(a: Any) {
+    if (a is Runnable) {
+        a as () -> Unit
+        J().run1(a)
+    }
+}
+
+fun test6(a: Any) {
+    a as () -> Unit
+    J().run1(a)
+}
+
+fun test7(a: (Int) -> Int) {
+    a as () -> Unit
+    J().run1(a)
+}
+
+fun test8(a: () -> Unit) {
+    J().run1(J.id(a))
+}
+
+fun test9() {
+    J().run1(::test9)
+}
+
+// FILE: J.java
+public class J {
+    public static void runStatic(Runnable r) {}
+
+    public void run1(Runnable r) {}
+
+    public void run2(Runnable r1, Runnable r2) {}
+
+    public static <T> T id(T x) { return x; }
+}