Hot statistic and hot scheduler issue list

## Performance
- [x] https://github.com/tikv/pd/issues/5692
- [ ] https://github.com/tikv/pd/issues/3725
- [ ] https://github.com/tikv/pd/issues/5713
- [ ] speed up to create operator in big cluster

## Statistic
- [x] #4042
- [ ] https://github.com/tikv/pd/issues/2497
- [ ] https://github.com/tikv/pd/issues/4481
- [x] https://github.com/tikv/pd/issues/3158
- [ ] https://github.com/tikv/pd/issues/3084
- [ ] https://github.com/tikv/pd/issues/5717

## Why no hot-scheduler operator?
- [X] https://github.com/tikv/pd/issues/4529
- [ ] https://github.com/tikv/tikv/issues/13461
- [x] #3098
- [ ] https://github.com/tikv/pd/issues/8944
- [ ] https://github.com/tikv/pd/issues/4041
- [x] https://github.com/tikv/pd/issues/6645

## Why has hot-scheduler operator?
- [x] https://github.com/tikv/pd/issues/3919
- [ ] https://github.com/tikv/pd/issues/5559
- [x] https://github.com/tikv/pd/issues/3298
- [x] https://github.com/tikv/pd/issues/6297
- [x] https://github.com/tikv/pd/pull/6314

## Reduce schedule cost
- [ ] https://github.com/tikv/pd/issues/5465
- [ ] https://github.com/tikv/pd/issues/3852
- [ ] https://github.com/tikv/pd/issues/2999
- [ ] https://github.com/tikv/pd/issues/3842
- [ ] https://github.com/tikv/pd/issues/662

## Dimension selection
- [x] #5718
- [ ] https://github.com/tikv/pd/issues/4612
- [ ] https://github.com/tikv/pd/issues/4513
- [X] https://github.com/tikv/pd/issues/3869
- [x] https://github.com/tikv/pd/issues/1432

## Dimension conflict
- [x] https://github.com/tikv/pd/issues/5446
- [X] https://github.com/tikv/pd/issues/4332
- [x] https://github.com/tikv/pd/issues/4949
- [x] https://github.com/tikv/pd/issues/4628

## Expectation and variance
- [ ] https://github.com/tikv/pd/issues/2168
- [ ] https://github.com/tikv/pd/issues/5545
- [x] https://github.com/tikv/pd/issues/3830

## split
- [x] https://github.com/tikv/pd/pull/6281
- [x] https://github.com/tikv/pd/pull/6618
### Load base split
- [ ] https://github.com/tikv/pd/issues/5267
- [ ] hot scheduler can create split operator

## Metrics, logs and pd-ctl
- [x] https://github.com/tikv/pd/issues/5643
- [x] https://github.com/tikv/pd/issues/4350
- [ ] https://github.com/tikv/pd/issues/4993
- [x] https://github.com/tikv/pd/issues/4607
- [ ] https://github.com/tikv/pd/issues/3049
- [ ] https://github.com/tikv/pd/issues/5733
- [ ] https://github.com/tikv/pd/issues/8817

## Config
- [ ] https://github.com/tikv/pd/issues/3943
- [ ] https://github.com/tikv/pd/issues/5155
- [ ] https://github.com/tikv/pd/issues/5732
- [x] #5698
- [x] #5701
- [ ] https://github.com/tikv/pd/issues/5897

## Refactor
- [x] #4477
- [x] #5708
- [x] #5709

## Tools
- [ ] https://github.com/tikv/pd/issues/3222
- [ ] https://github.com/tikv/pd/issues/3030
- [ ] https://github.com/tikv/pd/issues/2501

## Related Problem
#### Cold peer
- [ ] https://github.com/tikv/pd/issues/4351
- [ ] https://github.com/tikv/pd/issues/5602
#### Collect TiDB Info
- [ ] cached table and copr cache