Add GatheringTaskGroup class for Python 3.10 and below

[albireox]

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[codecov]

Codecov Report

Attention: Patch coverage is 86.95652% with 3 lines in your changes missing coverage. Please review.

Project coverage is 93.0%. Comparing base (f050824) to head (7bd25ce).
Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/sdsstools/utils.py	87.0%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            main     #52     +/-   ##
=======================================
- Coverage   93.2%   93.0%   -0.2%     
=======================================
  Files          6       6             
  Lines        616     639     +23     
  Branches     135     138      +3     
=======================================
+ Hits         574     594     +20     
- Misses        19      21      +2     
- Partials      23      24      +1     

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