Replace derivative with derive-where

[laniakea64]

Running cargo audit on just repo gives the following warnings -

Crate:     ansi_term
Version:   0.12.1
Warning:   unmaintained
Title:     ansi_term is Unmaintained
Date:      2021-08-18
ID:        RUSTSEC-2021-0139
URL:       https://rustsec.org/advisories/RUSTSEC-2021-0139
Dependency tree:
ansi_term 0.12.1
└── just 1.36.0

Crate:     derivative
Version:   2.2.0
Warning:   unmaintained
Title:     `derivative` is unmaintained; consider using an alternative
Date:      2024-06-26
ID:        RUSTSEC-2024-0388
URL:       https://rustsec.org/advisories/RUSTSEC-2024-0388
Dependency tree:
derivative 2.2.0
└── just 1.36.0

warning: 2 allowed warnings found

This PR fixes one of these two warnings by replacing derivative with derive-where, which is how rustc handled this.

[casey]

Nice, great PR! If you look at the Cargo.lock changes, you can also see that this gets rid of a dependency on syn v1, since derive_where uses syn v2. So this should speed up builds a bit too, since syn is a heavy dependency.

[casey]

Just measured it and build time went down from ~34.5s to ~32.5 seconds.