feat(search): pin Foyer and add split-range disk cache config

[congx4]

This is the first slice of a Foyer disk cache for exact split footer and body ranges. Follow-up PRs will add the cache key codec, Foyer device, and searcher wiring.

Summary

• Pin Foyer 0.22.3 and mixtrics 0.2.5, declare them on quickwit-storage, and regenerate LICENSE-3rdparty.csv.
• Add validated searcher.split_range_disk_cache config (disabled by default). write_policy defaults to write-on-eviction when omitted.

Test plan

• cargo check -p quickwit-storage
• cargo test -p quickwit-config split_range_disk_cache
• cargo clippy -p quickwit-config -p quickwit-storage --all-features --tests -- -D warnings
• cargo +nightly fmt --all -- --check
• CI unit tests and license check

Made with Cursor

[congx4]

Superseded by #6781, which preserves this work in a clean five-commit history rebased onto main.