config history diff, collapse identical rows

[shengbinxu]

What is the purpose of the change

#12587

Brief changelog

When using CodeMirror's mergeView to compare two versions of code, configure it to collapse identical lines, making it easier to visually focus on the differing lines.

Verifying this change

The folding effect is as follows:

The effect after displaying is as follows:

Follow this checklist to help us incorporate your contribution quickly and easily:

• Make sure there is a Github issue filed for the change (usually before you start working on it). Trivial changes like typos do not require a Github issue. Your pull request should address just this issue, without pulling in other changes - one PR resolves one issue.
• Format the pull request title like [ISSUE #123] Fix UnknownException when host config not exist. Each commit in the pull request should have a meaningful subject line and body.
• Write a pull request description that is detailed enough to understand what the pull request does, how, and why.
• Write necessary unit-test to verify your logic correction, more mock a little better when cross module dependency exist. If the new feature or significant change is committed, please remember to add integration-test in test module.
• Run mvn -B clean package apache-rat:check findbugs:findbugs -Dmaven.test.skip=true to make sure basic checks pass. Run mvn clean install -DskipITs to make sure unit-test pass. Run mvn clean test-compile failsafe:integration-test to make sure integration-test pass.

[CLAassistant]

All committers have signed the CLA.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 69.68%. Comparing base (38a204c) to head (49a98e2).

Additional details and impacted files

@@              Coverage Diff              @@
##             develop   #12608      +/-   ##
=============================================
+ Coverage      69.67%   69.68%   +0.01%     
- Complexity      9423     9433      +10     
=============================================
  Files           1275     1275              
  Lines          41232    41232              
  Branches        4374     4374              
=============================================
+ Hits           28728    28733       +5     
+ Misses         10424    10420       -4     
+ Partials        2080     2079       -1     

see 26 files with indirect coverage changes

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