optimise adding projections and indexes in one statement, to avoid er…

[stephen-up]

Sometimes we get this error. It looks like it happens more when a table has lots of projections or indexes.

 Code: 517.
    DB::Exception: Metadata on replica is not up to date with common metadata in Zookeeper.
    It means that this replica still not applied some of previous alters. Probably too many
    alters executing concurrently (highly not recommended).

This PR changes it from issuing an alter statement per index/projection to issuing a single statement adding all indexes and projections.

For additional context. We have been running the previous code in production for a few months without problems, but have recently noticed an increase in 517 errors.