feat: share ExtensionGetter Bean with plugins for extension retrieval

[LIlGG]

What type of PR is this?

/kind improvement
/area core
/milestone 2.18.x

What this PR does / why we need it:

通过将 ExtensionGetter Bean 共享到给插件的 ApplicationContext，插件能够方便地使用该 Bean 来获取扩展。此更改确保插件具有可靠的扩展访问方式，从而促进系统内更好的模块化和可扩展性。

Which issue(s) this PR fixes:

Fixes #6357

Does this PR introduce a user-facing change?

将 ExtensionGetter Bean 共享给插件使用，以便插件可以通过它来获取扩展

[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

All modified and coverable lines are covered by tests ✅

Project coverage is 58.35%. Comparing base (bc10336) to head (fb519c3).
Report is 82 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6365      +/-   ##
============================================
+ Coverage     54.51%   58.35%   +3.84%     
- Complexity     3523     3766     +243     
============================================
  Files           646      646              
  Lines         21862    21986     +124     
  Branches       1528     1546      +18     
============================================
+ Hits          11917    12829     +912     
+ Misses         9328     8535     -793     
- Partials        617      622       +5     

☔ View full report in Codecov by Sentry.
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[guqing]

/retitle feat: share ExtensionGetter Bean with plugins for extension retrieval

[guqing]

/lgtm

[f2c-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: guqing

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[guqing]

@LIlGG 此 PR 需要增加开发者文档，以告知插件开发者如何使用 ExtensionGetter 来扩展自己的插件功能

[LIlGG]

@LIlGG 此 PR 需要增加开发者文档，以告知插件开发者如何使用 ExtensionGetter 来扩展自己的插件功能

好，我去补充一下相关文档。