fix(NcRichText): do not render nested links in markdown

[Antreesy]

☑️ Resolves

• Extracted from fix(NcRichText): render invalid relative markdown links as external #8397
• with autolink + useMarkdown props [href2](href1) syntax is rendered as <a href1><a href2>href2</a></a> instead of href2 being a plain text
• deep nested links also respected

🖼️ Screenshots

🏚️ Before	🏡 After

🏁 Checklist

• ⛑️ Tests are included or are not applicable
• 📘 Component documentation has been extended, updated or is not applicable
• 2️⃣ Backport to stable8 for maintained Vue 2 version or not applicable

[codecov]

Codecov Report

❌ Patch coverage is 95.23810% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 54.69%. Comparing base (7b8d777) to head (7fda70f).
⚠️ Report is 107 commits behind head on main.

Files with missing lines	Patch %	Lines
src/components/NcRichText/autolink.ts	91.66%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8449      +/-   ##
==========================================
+ Coverage   54.09%   54.69%   +0.60%     
==========================================
  Files         104      104              
  Lines        3398     3406       +8     
  Branches      989      994       +5     
==========================================
+ Hits         1838     1863      +25     
+ Misses       1321     1304      -17     
  Partials      239      239              

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