fix: Button pseudo-element (before) not adapting to the btn-border-width when loading

[jjanssen]

[中文版模板 / Chinese template]

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• New feature
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🔗 Related issue link

💡 Background and solution

Currently when setting a custom @btn-border-width the loading state does not take this into consideration (which is having a fixed -1px definition). Visually this causes the original color to show as an additional outline which does not show in the 1px state.

How it currently renders (3px as an example)

How I expect it to render

📝 Changelog

Language	Changelog
🇺🇸 English	Fix: Button pseudo-element (before) not adapting to the btn-border-width for its loading state
🇨🇳 Chinese

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• 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

[ant-design-bot]

[github-actions]

Size Change: 0 B

Total Size: 788 kB

ℹ️ View Unchanged

Filename	Size	Change
./dist/antd-with-locales.min.js	312 kB	0 B
./dist/antd.compact.min.css	66.9 kB	0 B
./dist/antd.dark.min.css	68.2 kB	0 B
./dist/antd.min.css	66.9 kB	0 B
./dist/antd.min.js	274 kB	0 B

_{compressed-size-action}

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[codecov]

Codecov Report

Merging #28886 (4f1e3a7) into master (0747b3c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #28886   +/-   ##
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  Coverage   99.98%   99.98%           
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  Files         393      393           
  Lines        7444     7444           
  Branches     2086     2086           
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  Hits         7443     7443           
  Misses          1        1           

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