Move some tests from boxWithStdlib/ to box/

Move those tests which do not require neither stdlib nor reflect

compiler/testData/codegen/box/callableReference/property/kt6870_privatePropertyReference.kt

@@ -0,0 +1,22 @@
+class Test {
+    private var iv = 1
+
+    public fun exec() {
+        val t = object : Thread() {
+            override fun run() {
+                Test::iv.get(this@Test)
+                Test::iv.set(this@Test, 2)
+            }
+        }
+        t.start()
+        t.join(1000)
+    }
+
+    fun result() = if (iv == 2) "OK" else "Fail $iv"
+}
+
+fun box(): String {
+    val t = Test()
+    t.exec()
+    return t.result()
+}