Merge boxWithStdlib testData into box, delete BoxWithStdlib test

compiler/testData/codegen/box/jvmField/capturePackageFields.kt

@@ -0,0 +1,15 @@
+// WITH_RUNTIME
+
+@JvmField public val publicField = "1";
+@JvmField internal val internalField = "23";
+
+fun test(): String {
+    return {
+        publicField + internalField
+    }()
+}
+
+
+fun box(): String {
+    return if (test() == "123") return "OK" else "fail"
+}