Add a test that memory is reused with a long lived allocation

This test fails for the bump allocator because it can only free the complete heap at once, which is prevented by the single long-lived allocation.

tests/heap_allocation.rs

@@ -58,6 +58,18 @@ fn many_boxes() {
     serial_println!("[ok]");
 }
 
+#[test_case]
+fn many_boxes_long_lived() {
+    serial_print!("many_boxes_long_lived... ");
+    let long_lived = Box::new(1); // new
+    for i in 0..HEAP_SIZE {
+        let x = Box::new(i);
+        assert_eq!(*x, i);
+    }
+    assert_eq!(*long_lived, 1); // new
+    serial_println!("[ok]");
+}
+
 #[panic_handler]
 fn panic(info: &PanicInfo) -> ! {
     blog_os::test_panic_handler(info)