chore: update lance dependency to v7.0.0

[lance-community]

Summary

• Updates the Lance Rust dependency declarations in Cargo.toml from 6.0.0 to 7.0.0 for:
  • lance
  • lance-arrow
  • lance-core
  • lance-index
  • lance-linalg
  • lance-namespace
  • lance-namespace-impls
  • lance-table
• Preserves the existing feature flags and does not add a [patch.crates-io] override.
• Triggering Lance tag: refs/tags/v7.0.0

Resolver Notes

• The Lance v7.0.0 tag declares these crates as 7.0.0 and continues to use Arrow 58.0.0 and DataFusion 53.0.0, so the existing Arrow/DataFusion pins in this repository appear aligned.
• Cargo.lock could not be updated because crates.io currently resolves the requested Lance crates only up to 6.0.1; cargo update -p lance --precise 7.0.0 fails before lockfile generation with no matching package named lance found.
• No git dependency or crates.io patch override was added because this PR is constrained to crates.io stable releases only.

Checks

• cargo fmt --all succeeded.
• cargo check --manifest-path Cargo.toml failed during dependency resolution because lance = 7.0.0 is not available in the crates.io index yet.
• cargo clippy --manifest-path Cargo.toml --all-targets failed for the same dependency-resolution reason.