feat(inspect): add core metadata tables for inspect module

[xbattlax]

Summary

Implement 10 new metadata table types for the inspect module, addressing the metadata tables epic #823.

Changes

• Add crates/iceberg/src/inspect/refs.rs:

  • RefsTable showing all branches and tags with retention policies
  • Reads from TableMetadata.refs HashMap

• Add crates/iceberg/src/inspect/history.rs:

  • HistoryTable showing snapshot log with ancestry tracking
  • Computes is_current_ancestor by walking parent chain from current snapshot

• Add crates/iceberg/src/inspect/metadata_log_entries.rs:

  • MetadataLogEntriesTable showing metadata file history
  • Appends current metadata entry with snapshot/schema/sequence info

• Add crates/iceberg/src/inspect/files.rs with shared infrastructure:

  • files_schema() building dynamic schema with partition struct
  • scan_files() for current snapshot manifest scanning
  • scan_all_files() for all-snapshot scanning with manifest path deduplication
  • ContentFilter enum for data-only, deletes-only, or all content
  • FilesTable, DataFilesTable, DeleteFilesTable as thin wrappers

• Add crates/iceberg/src/inspect/all_manifests.rs:

  • AllManifestsTable iterating manifests across all snapshots
  • Adds reference_snapshot_id field to track which snapshot references each manifest

• Add crates/iceberg/src/inspect/all_files.rs:

  • AllFilesTable, AllDataFilesTable, AllDeleteFilesTable
  • Thin wrappers around scan_all_files() with different content filters

• Update crates/iceberg/src/inspect/metadata_table.rs:

  • Add AllManifests, AllFiles, AllDataFiles, AllDeleteFiles, History, MetadataLogEntries, Refs, Files, DataFiles, DeleteFiles to MetadataTableType enum
  • Add accessor methods on MetadataTable

• Update crates/integrations/datafusion/src/table/metadata_table.rs:

  • Add match arms for all new MetadataTableType variants in schema and scan

• Update crates/iceberg/src/scan/mod.rs:

  • Add setup_all_snapshot_manifest_files() test helper for all-snapshot tests

Notes

This matches the Java Iceberg implementation's metadata table types:

• Group A (metadata-only, no I/O): refs, history, metadata_log_entries
• Group B (file-level, shared infra): files, data_files, delete_files
• Group C (all-snapshot variants): all_manifests, all_files, all_data_files, all_delete_files

Remaining tables (all_entries, partitions, position_deletes) are blocked or deferred:

• all_entries depends on ENTRIES PR feat: Support metadata table "Entries"  #863
• partitions requires complex aggregation logic
• position_deletes requires reading delete file contents (needs design discussion)

Part of #823