build: lift workspace MSRV further to 1.85 for criterion's clap_lex

The first MSRV bump to 1.80 fixed the rayon-core floor but ran into a
second transitive-dep floor on the same CI run:

    error: failed to parse manifest at clap_lex-1.1.0/Cargo.toml
    Caused by: feature `edition2024` is required
    The package requires the Cargo feature called `edition2024`, but
    that feature is not stabilized in this version of Cargo (1.80.1).

clap_lex 1.1.0 is pulled in by criterion (dev-dep on the wickra crate)
via clap 4.6 -> clap_builder 4.6 -> clap_lex 1.1. edition2024 was
stabilized in Rust 1.85, so lift the workspace MSRV one more step. The
1.85 floor subsumes the rayon-core 1.80 requirement; bindings/node
stays at 1.88 (napi-build) which already covers everything below it.

Also fix the fuzz job: cargo-fuzz defaulted to building for
x86_64-unknown-linux-musl, which is not installed on the GitHub-hosted
ubuntu runner. Pass --target x86_64-unknown-linux-gnu explicitly on
every cargo fuzz run invocation so it builds for the actual host
target.

Cargo.toml

@@ -15,7 +15,7 @@ exclude = ["fuzz"]
 version = "0.2.0"
 authors = ["kingchenc <kingchencp@gmail.com>"]
 edition = "2021"
-rust-version = "1.80"
+rust-version = "1.85"
 license = "PolyForm-Noncommercial-1.0.0"
 repository = "https://github.com/kingchenc/wickra"
 homepage = "https://github.com/kingchenc/wickra"