DAL: Enhancements on the batching of shards

What

Several improvements to MR !18848 (merged), especially to address !18848 (comment 2741326691):

• use of disable_shard_validation,
• be able to profile it.

Furthermore, I moved the type of the batch from list to hash table to avoid treating duplicates of received shards.

Why

Since MR already took quite a long time to be merged, I do not want to add features in it.