K1/K2: add test for Future.get case

compiler/testData/diagnostics/tests/j+k/futureGet.kt

@@ -0,0 +1,18 @@
+// FIR_IDENTICAL
+// FULL_JDK
+// JVM_TARGET: 1.8
+
+import java.util.concurrent.Future
+import java.util.concurrent.atomic.AtomicReference
+
+fun foo(future: Future<String?>) {
+    future.get()<!UNSAFE_CALL!>.<!>length
+}
+
+fun bar(threadLocal: ThreadLocal<String?>) {
+    threadLocal.get()<!UNSAFE_CALL!>.<!>length
+}
+
+fun baz(ref: AtomicReference<String?>) {
+    ref.get()<!UNSAFE_CALL!>.<!>length
+}