[SUPPORT] Should we introduce extensible simple bucket index ?

Currently we have two types of buck engines：
- Simple: fixed bucket number
- Consistent hash: adjust bucket num by consistent hash relation

When user build a table with simple bucket index. The amount of data in each bucket can get larger over time, affecting the performance of compaction. However, users have no way to adjust the number of buckets in real time except to delete the table and rebuild.
So do we need to provide a way to dynamically adjust the bucket count?
Bucket resizing should not block reading and writing. We can use clustering to adjust the number of buckets, and we can use a dual write for new writes during resizing execution to ensure data consistency.

Why don't we use Consistent-Hash bucket engine?
- The number of buckets can only be increased or decreased one by one
- It is difficult to provide a bucket join to the query engine because of the complex mapping between hash and bucket

So should we introduce extensible simple bucket? Welcome to the discussion！

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