Iceberg data tables whose names end with a metadata-table name fall back to Spark #6719

Describe the bug

CometScanRule.isIcebergMetadataTable matches the table name with endsWith against the metadata table names (files, snapshots, history, entries, manifests, partitions, ...) with no separator. Any ordinary Iceberg table whose name ends with one of those words is treated as a metadata table and falls back to Spark with Iceberg Metadata tables are not supported, for example user_files, order_history, daily_partitions, or a table named snapshots.

val name = scanExec.table.name().toLowerCase(Locale.ROOT)
metadataTableSuffix.exists(name.endsWith)

Steps to reproduce

CREATE TABLE cat.db.user_files (id INT, name STRING) USING iceberg;
INSERT INTO cat.db.user_files VALUES (1, 'a'), (2, 'b');
SELECT * FROM cat.db.user_files;

With spark.comet.scan.icebergNative.enabled=true and spark.comet.explain.fallback.enabled=true the scan is reported as:

BatchScan cat.db.user_files [COMET: Iceberg Metadata tables are not supported]

The same table named users gets CometIcebergNativeScan.

Expected behavior

Only real metadata tables (cat.db.user_files.files, ...metadata.json#files) should fall back.

Additional context

Proposed fix: recognize a metadata table by its Iceberg type. Every metadata table extends org.apache.iceberg.BaseMetadataTable, and the table is reachable through the existing IcebergReflection.getTable(scan). Fall back to a whole-segment name match (.files, #files) only when the table cannot be reached. Happy to open a PR with a test covering user_files, snapshots and order_history plus a real .files read.