refactor: add uniqueness check for local thumbnail original links and dimensions to avoid duplication

[guqing]

What type of PR is this?

/kind improvement
/area core
/milestone 2.20.x

What this PR does / why we need it:

对本地缩略图的原图链接和尺寸增加唯一性检查避免重复

Does this PR introduce a user-facing change?

对本地缩略图的原图链接和尺寸增加唯一性检查避免重复

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

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[codecov]

Codecov Report

Attention: Patch coverage is 31.25000% with 11 lines in your changes missing coverage. Please review.

Project coverage is 57.22%. Comparing base (eff73dc) to head (79de0d5).
Report is 53 commits behind head on main.

Files with missing lines	Patch %	Lines
...ore/attachment/impl/LocalThumbnailServiceImpl.java	11.11%	8 Missing ⚠️
.../app/core/attachment/extension/LocalThumbnail.java	0.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #7031      +/-   ##
============================================
+ Coverage     56.99%   57.22%   +0.23%     
- Complexity     3999     4007       +8     
============================================
  Files           714      712       -2     
  Lines         24110    24154      +44     
  Branches       1585     1590       +5     
============================================
+ Hits          13742    13823      +81     
+ Misses         9756     9716      -40     
- Partials        612      615       +3     

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[sonarcloud]

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 SonarQube Cloud

[ruibaby]

/lgtm