Move away from `bincode` create

[marxin]

Due to a doxxing and harassment incident, development on bincode has ceased. No further releases will be published on crates.io.

We should start using one of the recommended alternatives: postcard or rkyv.

CC: @Arshia001

[Arshia001]

They also mentioned the crate hasn't had any changes for years, and that it's stable as-is. I'd delay this until cargo-deny starts complaining, since it doesn't look like anything bad can come of just keeping it.

[marxin]

https://rustsec.org/advisories/RUSTSEC-2025-0141