api,pd-ctl: support endKey in ScanRegions http interface

[IcePigZDB]

Development Task

Tracking Issue: pingcap/tidb/pull/28330

Support endKey in http interface regions/key and adjust the pdctl region command region startKey to region keysaccordingly. This is originally proposed as a precondition of the push down optimisation of infomation_schema.tikv_region_status.

• support endKey in ScanRegions http interface api,pd-ctl: support endKey in ScanRegions http interface #4142
• supplement ScanRegions http interface api,pd-ctl: foramte scanRegions api and fix a index out of range bug in relevant pdctl command #4371
• relevant docs tools: update the usage of region startkey to region keys pingcap/docs#6951
• relevant docs-cn tools: update the usage of region startkey to region keys pingcap/docs-cn#7637
• docs-cn typo tools: fix region keys typo pingcap/docs-cn#8485

Previous code is involved in v5.4.0.
In the current implementation of scanRegions , the default limit is defaultRegionLimit(16) without endkey and noRegionLimit(-1) with endkey.

Use this command to query all Regions in a given range [startkey, endkey). It supports range without endKey, the default value of limit is 16 without endKey and -1 (no limit) with endKey.

• When one try to use startKey = a, endKey = "" try to get all regions in [a, ), the default limit is defaultRegionLimit(16), need to set limit = -1 to get all regions, this is inconsistent with the case where endKey is not empty.
• No default limit when using pd-ctl to query endKey may cause a lot of network IO cost.

For these two reasons, tend to set the default limit with endKey to defaultRegionLimit(16) the same as without endKey. One can set limit = -1 to get all regions.

• code pr api: set scanregions with endkey default limit as 16 #4674
• doc-cn tools: chagen scanregions endkey default limit pingcap/docs-cn#8607
• doc update it's added here tools: update the usage of region startkey to region keys pingcap/docs#6951