feat(Input.Search): add loading prop

[shaodahong]

🤔 This is a ...

• New feature
• Bug fix
• Site / document update
• Component style update
• TypeScript definition update
• Refactoring
• Code style optimization
• Test Case
• Branch merge
• Other (about what?)

🔗 Related issue link

Fixed #14538

💡 Background and solution

📝 Changelog

Language	Changelog
🇺🇸 English	add search box loading prop
🇨🇳 Chinese	新增搜索框 loading prop

☑️ Self Check before Merge

• Doc is updated/provided or not needed
• Demo is updated/provided or not needed
• TypeScript definition is updated/provided or not needed
• Changelog is provided or not needed

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View rendered components/input/demo/search-input-loading.md
View rendered components/input/index.en-US.md
View rendered components/input/index.zh-CN.md

[tests-checker]

Could you please add tests to make sure this change works as expected?

[netlify]

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[buildsize]

File name	Previous Size	New Size	Change
package-lock.json	851.16 KB	848.68 KB	-2.48 KB (0%)

[codecov]

Codecov Report

Merging #18771 into feature will increase coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           feature   #18771      +/-   ##
===========================================
+ Coverage    96.78%   96.78%   +<.01%     
===========================================
  Files          281      281              
  Lines         7548     7558      +10     
  Branches      2102     2064      -38     
===========================================
+ Hits          7305     7315      +10     
  Misses         241      241              
  Partials         2        2

Impacted Files	Coverage Δ
components/input/Search.tsx	100% <100%> (ø)	⬆️

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[afc163]

还有 loading 时不再触发 onSearch 和其他搜索交互，类似 Button 的 loading，可以用于防抖。