Test "mem::uninit_write_slice_cloned_no_drop" leaks memory

[RalfJung]

The test mem::uninit_write_slice_cloned_no_drop added in #79607 leaks memory, which makes a Miri run of the test suite fail:

running 1 test
test mem::uninit_write_slice_cloned_no_drop ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 1176 filtered out

The following memory was leaked: alloc1884656 (Rust heap, size: 16, align: 8) {
    01 00 00 00 00 00 00 00 01 00 00 00 00 00 00 00 │ ................
}

Running Miri on the test suite is helpful to find bugs, so we should avoid deliberate leaks to still be able to detect accidental ones. Can the test be changed to use some other means of ensuring that drop is not called, e.g. with a Bomb type?

struct Bomb;

impl Drop for Bomb {
  fn drop(&mut self) { panic!(); }
}

Cc @drmeepster

[beepster4096]

@rustbot claim

I made the test I should fix it

[RalfJung]

@drmeepster thanks. :-) Let me know if you need any help.