statistics: support dump/load correlation of histogram

[eurekaka]

What problem does this PR solve?

Stats dumped using HTTP API does not contain order correlation of columns.

What is changed and how it works?

Add dump/load support for correlation of histogram.

Check List

Tests

• Unit test

Code changes

• Has exported function/method change

Side effects

• Breaking backward compatibility: stats dumped from old versions can be successfully loaded into current version, while stats dumped from current version cannot be loaded into old versions;

Related changes

• Need to update the documentation

[eurekaka]

/run-all-tests

[eurekaka]

/run-integration-ddl-test

[codecov]

Codecov Report

Merging #10573 into master will increase coverage by 0.003%.
The diff coverage is 100%.

@@               Coverage Diff               @@
##             master     #10573       +/-   ##
===============================================
+ Coverage   77.3275%   77.3306%   +0.003%     
===============================================
  Files           413        413               
  Lines         87322      87378       +56     
===============================================
+ Hits          67524      67570       +46     
- Misses        14605      14606        +1     
- Partials       5193       5202        +9

[alivxxx]

LGTM

[XuHuaiyu]

LGTM