Update Rust crate hashbrown to 0.17.0.

Update Rust crate indexmap to 2.14.0 (2026-04-09).

• MSRV: Rust 1.85.0 or later is now required.
• Updated the hashbrown dependency to 0.17.
• Made more map::Slice methods const: new_mut, first_mut, last_mut, split_at_mut, split_at_mut_checked, split_first_mut, split_last_mut

Update Rust crates rkyv / rkyv_derive to 0.8.16.

Update oxipng to 10.1.1.

• [Performance] Improve Bigrams performance, giving notably faster results at lower levels.
• [Improvement] Change --np flag to also prevent conversion to indexed from other color types.
• [Improvement] Improve support for recompressing ICC profiles with high compression ratios.
• [Misc] Add warning when --ziwi exceeds --zi.
• [Build] Further reduce size of binaries.