sql/inspect: Support hash-sharded indexes in index consistency checks

INSPECT cannot check hash-sharded indexes for consistency. These indexes are currently filtered out during job creation.

Hash-sharded indexes have an implicit shard column (e.g., crdb_internal_x_shard_16) that must be included in LOOKUP JOIN conditions. The current INSPECT query generation (pkg/sql/inspect/index_consistency_check.go) builds join conditions only from user-visible columns, causing the query planner to fail with "could not produce a query plan conforming to the LOOKUP JOIN hint".

Note: this works in classic SCRUB because it uses FULL OUTER JOIN without hints, allowing the optimizer to choose hash/merge joins which don't require the shard column in join predicates.

Jira issue: CRDB-55106

Epic CRDB-55075