Tracking issues of restore performance improvement.

## Enhancement

Tracking issues of restore performance in different stage. basically we have 4 stages during restoartion.
```
1. Load Data from Storage.
2. Create DB/Tables.
3. Region Split & Scatter.
4. Download & Ingest SST Files.
```

- [x] (Stage 3) https://github.com/pingcap/tidb/issues/33937
- [x] https://github.com/pingcap/tidb/pull/48244
- [x] https://github.com/pingcap/tidb/pull/50255
- [x] (Stage 4)https://github.com/pingcap/tidb/issues/49886
- [x] https://github.com/pingcap/tidb/pull/49887
- [x] https://github.com/tikv/tikv/pull/16298

## Bugfixs
Functional issues
- [x] https://github.com/pingcap/tidb/issues/50471
- [x] https://github.com/pingcap/tidb/pull/50518
- [x] https://github.com/pingcap/tidb/issues/51078
- [x] https://github.com/pingcap/tidb/issues/51736
- [x] https://github.com/pingcap/tidb/pull/51777

Performance issues
- [x] https://github.com/pingcap/tidb/issues/50593
- [x] https://github.com/pingcap/tidb/issues/50566
- [x] https://github.com/pingcap/tidb/issues/50617
- [x] https://github.com/pingcap/tidb/issues/50613
- [x] https://github.com/pingcap/tidb/issues/50767
- [x] https://github.com/pingcap/tidb/issues/50772
- [x] https://github.com/pingcap/tidb/issues/51685
- [x] https://github.com/pingcap/tidb/issues/53532

Compatible issues
- [x] (checkpoint) https://github.com/pingcap/tidb/issues/50665
- [x] (checkpoint) https://github.com/pingcap/tidb/issues/50232
- [x] (statistic) https://github.com/pingcap/tidb/issues/50568

Enhancement
- [x] https://github.com/pingcap/tidb/pull/50877
- [x] https://github.com/pingcap/tidb/pull/51535
- [x] https://github.com/pingcap/tidb/pull/51578
- [x] https://github.com/pingcap/tidb/pull/51653