Increase the probability of balancing new regions

## Feature Request

### Describe your feature request related problem
There is an issue about the new region may have a low probability to be balanced，such as:
```
8
7 7
6 6 6
5 5 5 5
4 4 4 4 4
3 3 3 3 3 3
2 2 2 2 2 2 2
1 1 1 1 1 1 1 1
t1 t2 t3 t4 t5 t6 t7 t8
```
such as the above drawing, the y-axis represents the existing regions at that moment. region 8 only appears at time t8, the probability of R8 being selected in the entire sample space is very small.
this issue will lead to a scenario: import a new table into a big cluster, the region of this table will be unevenly distributed, which will bring some hot store issues.
### Describe alternatives you've considered
Empirically, We hope that the distribution of data is relatively random.

### Teachability, Documentation, Adoption, Migration Strategy
- Go
- Stochastic Processes / Probability theory