chore(msrv): Increase MSRV to 1.88

[szokeasaurusrex]

Bump the MSRV to 1.88 to allow dependency updates (see #968). I do not think this change requires a major version bump, as our MSRV policy states we try to support the last six months of Rust versions, and 1.88 is more than six months old.

Stacked on #969.

[lcian]

If you don't want to bump to 1.88, I believe it's also possible to address this by bumping to 1.85 and switching to edition = "2024" and therefore resolver = "3".
That way, cargo update should only pick versions of the deps that are compatible with that MSRV.

[szokeasaurusrex]

If you don't want to bump to 1.88, I believe it's also possible to address this by bumping to 1.85 and switching to edition = "2024" and therefore resolver = "3". That way, cargo update should only pick versions of the deps that are compatible with that MSRV.

This is probably a good idea, independently of this change. Although given that most of the Rust ecosystem is pretty good about keeping Rust updated, I see little reason to only increase MSRV to 1.85, and not 1.88, especially if 1.88 gives us newer dependency versions