[scratchpad] move_elements can double-free objects on panic

An issue was discovered in the scratchpad crate before 1.3.1 for Rust. The move_elements function can have a double-free upon a panic in a user-provided f function.

References

• https://nvd.nist.gov/vuln/detail/CVE-2021-28031
• https://rustsec.org/advisories/RUSTSEC-2021-0030.html
• https://github.com/okready/scratchpad/issues/1
• https://github.com/advisories/GHSA-3qm2-rfqw-fmrw