test: enhance Avatar component unit tests

[adaex]

Add unit tests for the Avatar component to cover various shapes, sizes, and states, as well as tests for the ref functionality and automatic font adjustment.

[Copilot]

Copilot reviewed 1 out of 1 changed files in this pull request and generated no comments.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.77%. Comparing base (e04f22e) to head (e1b97ae).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #329      +/-   ##
==========================================
+ Coverage   89.71%   89.77%   +0.05%     
==========================================
  Files         141      141              
  Lines        8393     8393              
  Branches     3447     3447              
==========================================
+ Hits         7530     7535       +5     
+ Misses        835      830       -5     
  Partials       28       28              

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[github-actions]

✨ PR Preview Link: https://preview-329-arco-design-mobile.surge.sh