chore: update lance dependency to v2.0.0 (stable only)

[Xuanwo]

Summary

• bump Lance Rust dependencies to stable 2.0.0 (from 2.0.0-rc.4)
• remove [patch.crates-io] overrides so Lance crates resolve from crates.io only
• keep CI updates stable-only:
  • ci/check_lance_release.py now filters to stable tags
  • codex-update-lance-dependency now rejects non-stable tags and explicitly forbids adding Lance [patch.crates-io]

Lockfile / Resolver Notes

• Cargo.lock now resolves Lance crates (lance*, fsst) from crates.io instead of git tag sources.
• itertools edge used by prost resolver moved from 0.11.0 to 0.14.0 in lockfile.

Validation

• cargo update -p lance -p lance-arrow -p lance-core -p lance-index -p lance-linalg -p lance-namespace -p lance-namespace-impls -p lance-table
• cargo check --manifest-path Cargo.toml
• python3 -m py_compile ci/check_lance_release.py
• rg -n "\[patch\.crates-io\]" Cargo.toml (no match)
• rg -n "git\+https://github.com/lance-format/lance" Cargo.lock (no match)

Triggering release tag

• v2.0.0