Upgrade to Python 3.10

[achimnol]

refs lablup/backend.ai#300

[codecov]

Codecov Report

Merging #103 (2ba3ab9) into main (9c4ee94) will increase coverage by 0.22%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #103      +/-   ##
==========================================
+ Coverage   75.75%   75.98%   +0.22%     
==========================================
  Files          23       23              
  Lines        3193     3210      +17     
==========================================
+ Hits         2419     2439      +20     
+ Misses        774      771       -3     

Impacted Files	Coverage Δ
src/ai/backend/common/etcd.py	82.90% <ø> (+0.22%)	⬆️
src/ai/backend/common/validators.py	70.30% <0.00%> (-0.26%)	⬇️
src/ai/backend/common/files.py	95.12% <0.00%> (+0.12%)	⬆️
src/ai/backend/common/logging.py	61.92% <0.00%> (+0.14%)	⬆️
src/ai/backend/common/plugin/__init__.py	91.01% <0.00%> (+0.31%)	⬆️
src/ai/backend/common/redis.py	76.52% <0.00%> (+1.76%)	⬆️
src/ai/backend/common/asyncio.py	80.43% <0.00%> (+2.17%)	⬆️
src/ai/backend/common/service_ports.py	97.36% <0.00%> (+2.77%)	⬆️

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[achimnol]

Closing in favor of #123.