feat(io): improve and document SheetsWriter

[AndreyMarkinPPC]

• improve spreadsheet sharing:
  • perform sharing only once during spreadsheet initialization
  • allow sharing with multiple email addresses
  • don't send notification
• initialize client only once
• document sheets writer usage

[codecov-commenter]

Codecov Report

❌ Patch coverage is 18.51852% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 89.88%. Comparing base (5ebb9d2) to head (382d3ce).
⚠️ Report is 132 commits behind head on main.

Files with missing lines	Patch %	Lines
libs/io/garf/io/writers/sheets_writer.py	12.00%	22 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #326      +/-   ##
==========================================
+ Coverage   88.23%   89.88%   +1.65%     
==========================================
  Files          61       76      +15     
  Lines        2600     3719    +1119     
==========================================
+ Hits         2294     3343    +1049     
- Misses        306      376      +70     

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