Spark: Extend V2 strategy support for view-related commands

[GGraziadei]

Follow-up from #14984 (comment).

What happens

ResolveViews resolves any UnresolvedTableOrView pointing at an Iceberg V2 view into a ResolvedV2View:

case u @ UnresolvedTableOrView(CatalogAndIdentifier(catalog, ident), _, _, _) =>
  ViewUtil.loadView(catalog, ident).map(view => ResolvedV2View(...)).getOrElse(u)

RewriteViewCommands then rewrites the view commands Iceberg owns, at parse time, into Iceberg-aware nodes: CreateView, DropView, RenameTable, DescribeRelation, ShowCreateTable, ShowTableProperties, ShowViews, and UnresolvedView. For those, ExtendedDataSourceV2Strategy has a matching case and planning succeeds.

Commands outside that set — SHOW COLUMNS, ANALYZE TABLE, and similar — still resolve to a ResolvedV2View, but the strategy has no case for a bare ResolvedV2View and falls through to case _ => Nil (ExtendedDataSourceV2Strategy.scala:193). The result is a planner failure rather than a clear unsupported-operation error.

Scope

This is not specific to the Spark 4.2 work. The same UnresolvedTableOrView case exists in spark/v4.0 and spark/v4.1 (ResolveViews.scala:59 in both), so any Spark module supporting Iceberg V2 views is affected. It reflects existing Spark-side V2 view limitations, and was deliberately left out of scope in #14984.

Temporary views are not affected: they are resolved before the extension rule runs, as established in the PR discussion.

Proposed work

• Decide, per command, whether Iceberg should add V2 strategy support or surface a clear unsupported-operation error naming the command and the view.
• Apply the outcome consistently across the spark/v4.x modules rather than only the newest one.
• Add coverage in TestViews, which currently exercises neither SHOW COLUMNS nor ANALYZE TABLE against a V2 view.

cc @manuzhang