FEAT: Add / remove a sub pool

[ChengjieLi28]

What do these changes do?

Related issue number

Fixes #53

Check code requirements

• tests added / passed (if needed)
• Ensure all linting tests pass

[codecov]

Codecov Report

Merging #54 (44e98af) into main (b153a14) will increase coverage by 0.25%.
The diff coverage is 96.87%.

@@            Coverage Diff             @@
##             main      #54      +/-   ##
==========================================
+ Coverage   88.82%   89.07%   +0.25%     
==========================================
  Files          47       47              
  Lines        3928     3991      +63     
  Branches      757      760       +3     
==========================================
+ Hits         3489     3555      +66     
  Misses        352      352              
+ Partials       87       84       -3     

Flag	Coverage Δ
unittests	88.90% <96.87%> (+0.25%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
python/xoscar/backends/communication/socket.py	97.20% <ø> (+0.46%)	⬆️
python/xoscar/backends/indigen/pool.py	94.57% <95.23%> (+1.23%)	⬆️
python/xoscar/backends/config.py	87.01% <100.00%> (+3.45%)	⬆️
python/xoscar/backends/test/pool.py	100.00% <100.00%> (+1.53%)	⬆️

... and 2 files with indirect coverage changes

📢 Have feedback on the report? Share it here.

[aresnow1]

LGTM