refactor: optimize key comparator for indicates key sort

[guqing]

What type of PR is this?

/kind improvement
/area core
/milestone 2.19.x

What this PR does / why we need it:

重构 KeyComparator 并通过更多的测试用例来确保排序功能的正确性

同时修复了可能存在溢出导致比较结果不正确的问题，目前：

1. 字符串长度比较：在 compareStrings 方法中，字符串的长度比较使用 Integer.compare，这部分代码不会产生整数溢出问题。
2. 数字部分的比较：在 compareNumbers 方法中，数字的比较是基于字符比较的（即逐位比较每个数字字符），没有涉及到将数3. 字字符串转化为 int 或 long 类型的操作，所以不会存在整数溢出问题。
3. 处理小数部分的比较：在 compareDecimalNumbers 方法中，类似地，比较操作也是基于字符的，不涉及到数值转换，因此也不存在整数溢出问题

Which issue(s) this PR fixes:

Fixes #6466

Does this PR introduce a user-facing change?

修复由于索引比较时可能出现整数溢出导致文章偶尔无法访问的问题

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[codecov]

Codecov Report

Attention: Patch coverage is 75.29412% with 21 lines in your changes missing coverage. Please review.

Project coverage is 57.99%. Comparing base (6cd8dc8) to head (aa326a8).
Report is 42 commits behind head on main.

Files with missing lines	Patch %	Lines
...va/run/halo/app/extension/index/KeyComparator.java	75.29%	12 Missing and 9 partials ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6555      +/-   ##
============================================
- Coverage     58.18%   57.99%   -0.19%     
- Complexity     3774     3912     +138     
============================================
  Files           651      670      +19     
  Lines         22125    22940     +815     
  Branches       1538     1572      +34     
============================================
+ Hits          12873    13305     +432     
- Misses         8641     9020     +379     
- Partials        611      615       +4     

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[ruibaby]

/lgtm

[JohnNiang]

/lgtm

[f2c-ci-robot]

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This pull-request has been approved by: JohnNiang

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