* s3tables: tag table entries and exclude views from table listings
* s3tables: add view CRUD operations
* iceberg: support view create, load, exists, drop, and list
* iceberg: support view update
* iceberg: test view error classification and metadata round-trip
* iceberg: pre-check existence and write view metadata only after create
* iceberg: map view namespace-not-found to 404
* iceberg: test view create namespace-404 and duplicate no-clobber
* s3tables: tag view metadata and entry type atomically
CreateView wrote ExtendedKeyMetadata and ExtendedKeyEntryType in two
UpdateEntry calls, so a partial failure could leave a view directory
untagged. Add setExtendedAttributes to set both in one UpdateEntry.
* iceberg: roll back view registration when metadata write fails
The metadata file is written after the catalog registers the view. If
that write fails, drop the just-created view so it doesn't linger
pointing at a missing metadata.json. Reuse the DeleteView path via a
shared dropView helper.
