Is your feature request related to a problem? Please describe.
Currently hash sharding is not allowed if an index is partitioned. But this would be a feature wildly wanted by users. For example an user asked if they can emulate hash-sharded index with partitioned table in discussion #74395

Describe the solution you'd like
Support hash-sharded indices with all the following partitioning cases.
(1) implicit partitioned index in regional by row tables (crdb_region is not part of the index columns)
(2) implicit partitioned index in partition all by tables (partitioning fields are not part of the index columns

Epic CRDB-7363