Support smart cast for nullability in LHS of class literal

#KT-16291 Fixed

compiler/testData/codegen/box/classLiteral/bound/smartCast.kt

@@ -0,0 +1,11 @@
+// KT-16291 Smart cast doesn't work when getting class of instance
+
+class Foo(val s: String) {
+    override fun equals(other: Any?): Boolean {
+        return other != null && other::class == this::class && s == (other as Foo).s
+    }
+}
+
+fun box(): String {
+    return if (Foo("a") == Foo("a")) "OK" else "Fail"
+}

compiler/testData/codegen/light-analysis/classLiteral/bound/smartCast.txt

@@ -0,0 +1,12 @@
+@kotlin.Metadata
+public final class Foo {
+    private final @org.jetbrains.annotations.NotNull field s: java.lang.String
+    public method <init>(@org.jetbrains.annotations.NotNull p0: java.lang.String): void
+    public method equals(@org.jetbrains.annotations.Nullable p0: java.lang.Object): boolean
+    public final @org.jetbrains.annotations.NotNull method getS(): java.lang.String
+}
+
+@kotlin.Metadata
+public final class SmartCastKt {
+    public final static @org.jetbrains.annotations.NotNull method box(): java.lang.String
+}