feat(Field): password field supports showing and hiding the password

[keeplearning66]

This PR is to close #13565

I added showPasswordIcon prop to support showing and hiding the password.

showPasswordIcon: used for users to set whether the password icon should be displayed
showPwdIcon: used for internal confirmation of whether the password icon should be displayed, as there may be situations where it is not necessary to show the password icon
passwordIcon: used to confirm the type of the password icon, which can be either eye-o or closed-eye
showPassword: used to confirm whether the password field should display the password
selectionInfo: used to record the cursor's position, and maintain focus when the password icon is clicked

After modification

20250725_090039.mp4

I have added the corresponding unit tests

[codecov-commenter]

Codecov Report

❌ Patch coverage is 75.00000% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.68%. Comparing base (ec5b45b) to head (b82fdab).
⚠️ Report is 177 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/vant/src/field/Field.tsx	75.00%	3 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #13567      +/-   ##
==========================================
+ Coverage   89.60%   89.68%   +0.08%     
==========================================
  Files         257      257              
  Lines        7013     7060      +47     
  Branches     1736     1750      +14     
==========================================
+ Hits         6284     6332      +48     
- Misses        384      386       +2     
+ Partials      345      342       -3     

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[001cici]

When will this function be available online?

[keeplearning66]

I'm not sure either — this PR still hasn't been reviewed.

[001cici]

您的文件已收到，谢谢！