Supports co-balance range group

## Description
the placement rules which can place the regions in the stores which meet the label constraint. but in some situations, we need the range to share the same balance strategy and the peers always place in the same node. such as https://github.com/pingcap/tidb/issues/19805

The range group can add or remove interleaved ranges, that's mean the range inside is not necessarily continuous. each range group shares the same statistics, balance strategy, and same placement, It can be seen as a single region, in the future, TiKV can support to make them into one raft group.

the workload example: https://github.com/pingcap/tidb/issues/19381
## SIG slack channel
- [#sig-scheduling](https://tikv-wg.slack.com/archives/C019JHX6G8H)

## Tasks
- [ ] Detail design
- [ ] Supports group unit
- [ ] Share the balance strategy and statistic for the group
- [ ] Supports the DDL like mentioned in https://github.com/pingcap/tidb/issues/19805

## Score
- 6600

## Mentor
- @Yisaer

## Recommended Skills
- Go