chore(deps): bump iceberg-rust (parallel file scanning) + standardize fork branch naming (spiceai#11328)

* chore(deps): bump iceberg-rust to parallel file scanning fork

Bumps the spiceai/iceberg-rust pin from e519b221 to b652de2e, picking up
the eager task-bucketing parallel-scan change (spiceai/iceberg-rust#42,
port of apache/iceberg-rust#2298).

IcebergTableProvider::scan() now plans files eagerly and distributes
FileScanTasks across min(target_partitions, n_files) DataFusion
partitions, so Iceberg file reads are scheduled concurrently instead of
through a single partition. Identity-partitioned tables additionally
declare Partitioning::Hash so downstream joins/aggregates can skip a
RepartitionExec.

No Spice code changes are required: Spice consumes the provider only via
IcebergTableProvider::try_new, and the change is internal to the scan
path. The fork preserves Spice's existing iceberg limit-pushdown.

* chore(deps): adopt spiceai-<iceberg>-df-<df> fork naming; re-pin to spiceai-0.9.1-df-53

Re-pins iceberg-rust to the renamed `spiceai-0.9.1-df-53` branch (rev
9e6e1a00) and bumps the version requirement to `=0.9.1` to match the
corrected crate version. Adds docs/dev/fork-branch-naming.md documenting
the `spiceai-<iceberg>-df-<datafusion>` convention.

The DF53 fork line was previously named `spiceai-0.9.0` but actually
tracks a post-0.9.1 `main` snapshot; the rename + version correction make
the branch name reflect its real contents.

* chore(deps): re-pin iceberg-rust to merged spiceai-0.9.1-df-53 commit

Fork PR spiceai/iceberg-rust#43 merged; re-pin from the branch head
(9e6e1a00) to the merge commit b8fc79d9 on spiceai-0.9.1-df-53.

* chore(deps): annotate iceberg pins with fork branch; drop naming doc

Address Copilot review on spiceai#11328: add `# branch: spiceai-0.9.1-df-53`
to the iceberg-rust pins (matching the convention used by
delta_kernel/duckdb/arrow). Remove docs/dev/fork-branch-naming.md per
review feedback (no separate doc).

Author: phillipleblanc

Cargo.lock

@@ -210,12 +210,12 @@ hf-hub = { version = "0.4", features = ["tokio"] }
 http = "1.3.1"
 httpdate = "1.0"
 humantime = "2.1.0"
-iceberg = "=0.9.0"
-iceberg-catalog-glue = "=0.9.0"
-iceberg-catalog-rest = "=0.9.0"
-iceberg-datafusion = "=0.9.0"
-iceberg-storage-opendal = { version = "=0.9.0", features = ["opendal-s3", "opendal-gcs", "opendal-fs"] }
-iceberg_test_utils = "=0.9.0"
+iceberg = "=0.9.1"
+iceberg-catalog-glue = "=0.9.1"
+iceberg-catalog-rest = "=0.9.1"
+iceberg-datafusion = "=0.9.1"
+iceberg-storage-opendal = { version = "=0.9.1", features = ["opendal-s3", "opendal-gcs", "opendal-fs"] }
+iceberg_test_utils = "=0.9.1"
 imap = { git = "https://github.com/jonhoo/rust-imap", rev = "6fe22ed11a1ccffe1799a73f48e589366d8d100f" }
 indexmap = "2"
 insta = { version = "1.46.3", features = ["filters"] }
@@ -455,12 +455,12 @@ tokio-rusqlite = { git = "https://github.com/spiceai/tokio-rusqlite.git", rev =
 # Tracking Issue: https://github.com/allan2/dotenvy/issues/113
 dotenvy = { git = "https://github.com/spiceai/dotenvy.git", rev = "e5cef1871b08003198949dfe2da988633eaad78f" }
 
-iceberg = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "e519b22193e44667dde7d461e3cac1798fa0c9e2" }
-iceberg-catalog-glue = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "e519b22193e44667dde7d461e3cac1798fa0c9e2" }
-iceberg-catalog-rest = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "e519b22193e44667dde7d461e3cac1798fa0c9e2" }
-iceberg-datafusion = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "e519b22193e44667dde7d461e3cac1798fa0c9e2" }
-iceberg-storage-opendal = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "e519b22193e44667dde7d461e3cac1798fa0c9e2" }
-iceberg_test_utils = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "e519b22193e44667dde7d461e3cac1798fa0c9e2" }
+iceberg = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "b8fc79d9717d8576a45e2bd49aee52967b763f1d" } # branch: spiceai-0.9.1-df-53
+iceberg-catalog-glue = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "b8fc79d9717d8576a45e2bd49aee52967b763f1d" } # branch: spiceai-0.9.1-df-53
+iceberg-catalog-rest = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "b8fc79d9717d8576a45e2bd49aee52967b763f1d" } # branch: spiceai-0.9.1-df-53
+iceberg-datafusion = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "b8fc79d9717d8576a45e2bd49aee52967b763f1d" } # branch: spiceai-0.9.1-df-53
+iceberg-storage-opendal = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "b8fc79d9717d8576a45e2bd49aee52967b763f1d" } # branch: spiceai-0.9.1-df-53
+iceberg_test_utils = { git = "https://github.com/spiceai/iceberg-rust.git", rev = "b8fc79d9717d8576a45e2bd49aee52967b763f1d" } # branch: spiceai-0.9.1-df-53
 
 # candle-* crates are already redirected to the spiceai/candle fork via the
 # [patch.crates-io] block higher up in this file. Keeping those here would be