Fix clippy warnings on newer Rust toolchains

[antiguru]

CI derives its toolchain from the rust-version field in the root Cargo.toml, which pins 1.97.1. Warnings that newer toolchains introduce therefore go unreported until someone builds locally. This change clears everything that Rust 1.98 reports, plus the deprecations that the current nightly adds on top.

Rust 1.98 extends clippy::extra_unused_lifetimes to higher-ranked binders in where-clauses, which flags three for<'a> binders whose lifetime never appears in the bound they introduce. Removing the binder leaves the bounds unchanged, because the parenthesized Fn sugar already introduces a fresh lifetime for each elided reference. The same toolchain also reports two unused imports and three clippy::useless_format calls. parser_err! calls to_string on a single-expression argument, so passing the literal directly still produces an owned String.

Nightly additionally deprecates the legacy numeric constants and constructors. max_value and min_value become the MAX and MIN associated constants, and std::usize::MAX becomes usize::MAX. Dropping the use std::i64 import in the Avro decoder is what silences the two warnings on i64::MAX and i64::MIN, because that import made the path resolve to the deprecated module instead of the primitive type.

Two groups of nightly warnings are left alone. The fetch_update to try_update rename is too recent to use while CI builds with 1.97.1, and the overflow evaluating the requirement notices come from the new trait solver hitting its recursion limit rather than from a defect in this code.

Note that this change does not close the gap that hid these warnings. CI keeps building with 1.97.1, so the next lint a newer toolchain adds will go unreported the same way. Bumping rust-version rebuilds the CI builder image and raises the declared minimum supported version, which belongs in its own change.

Release notes

No user-visible changes.

🤖 Posted by Claude Code

[ggevay]

Thank you!

[antiguru]

Thanks for the review!