[Iceberg] Add Iceberg crate dependencies

[gabotechs]

Introduces the empty datafusion-distributed-iceberg crate, its dependency set, and the corresponding lockfile updates.

This is the first layer of the Iceberg integration stack. The implementation follows in #595.

[shinzoxD]

The new workspace crate is not covered by the current CI commands. Because the workspace root is itself a package and there is no default-members entry, cargo metadata --no-deps reports only datafusion-distributed as a default member. The workflow runs cargo build, cargo test --features integration, and cargo clippy --all-targets --all-features without --workspace or -p datafusion-distributed-iceberg, so the green checks do not compile or lint this crate (or validate its dependency/feature combination); only cargo fmt --all reaches it.

Please add explicit CI coverage for datafusion-distributed-iceberg (or include it in the intended default-member/workspace commands) as part of introducing the crate. I also attempted the missing cargo check -p datafusion-distributed-iceberg --all-targets locally, but its fresh dependency build exceeded a three-minute bounded run, so I am not claiming a local compiler result.