[Test] Add diagnostic tests for smartcast in K2

List of issues:
KT-28806, KT-7186, KT-22997, KT-1982, KT-22996, KT-54443, KT-37308, KT-37115, KT-4113, KT-25747, KT-24779

compiler/testData/diagnostics/tests/smartCasts/nullableLambda.fir.kt

@@ -0,0 +1,56 @@
+// ISSUE: KT-4113
+// DIAGNOSTICS: -DEBUG_INFO_SMARTCAST
+class Test1(val lambda: (() -> String)?) {
+    fun foo() {
+        if (lambda != null) {
+            lambda.invoke()
+            lambda()
+        }
+    }
+}
+
+fun test2(lambda: (() -> String)?) {
+    if (lambda != null) {
+        lambda.invoke()
+        lambda()
+    }
+}
+
+class A
+operator fun A.invoke(): Unit = TODO()
+
+class Test3 {
+    val nullableCallableClass: A? = null
+    fun foo() {
+        if (nullableCallableClass != null) {
+            nullableCallableClass()
+        }
+    }
+}
+
+fun test4(nullableCallableClass: A?){
+    if (nullableCallableClass != null) {
+        nullableCallableClass()
+    }
+}
+
+class B {
+    operator fun invoke(s: String): (() -> String)? = TODO()
+    operator fun invoke(): (() -> String) = TODO()
+}
+
+class Test4 {
+    fun foo(a: B) {
+        if (a("") != null) {
+            a()()
+            <!UNSAFE_IMPLICIT_INVOKE_CALL!>a("")<!>()
+        }
+    }
+}
+
+fun test5(a: B) {
+    if (a("") != null) {
+        a()()
+        <!UNSAFE_IMPLICIT_INVOKE_CALL!>a("")<!>()
+    }
+}