feat(sftp): support multi-file uploads

[CoolLoong]

Enable multi-selection in the SFTP upload file picker

[codecov]

Codecov Report

❌ Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 54.53%. Comparing base (c914f22) to head (6eb7937).

Files with missing lines	Patch %	Lines
crates/gpui_sftp/src/view/table/actions.rs	0.00%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #41      +/-   ##
==========================================
- Coverage   54.53%   54.53%   -0.01%     
==========================================
  Files         159      159              
  Lines       54169    54170       +1     
==========================================
  Hits        29542    29542              
- Misses      24627    24628       +1     

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[iamazy]

Thanks