Add Python 3.10 support.

[ChrisCummins]

This bumps several dependencies to enable Python 3.10 support, and switches the default version of python used for single-python CI jobs from 3.9 to 3.10.

[codecov-commenter]

Codecov Report

Merging #752 (80879d4) into development (dd66b2c) will increase coverage by 0.37%. The diff coverage is 100.00%.

:exclamation: Current head 80879d4 differs from pull request most recent head 628fc03. Consider uploading reports for the commit 628fc03 to get more accurate results

@@               Coverage Diff               @@
##           development     #752      +/-   ##
===============================================
+ Coverage        88.84%   89.21%   +0.37%     
===============================================
  Files              130      130              
  Lines             7864     7912      +48     
===============================================
+ Hits              6987     7059      +72     
+ Misses             877      853      -24     

Impacted Files	Coverage Δ
compiler_gym/envs/gcc/gcc.py	93.50% <100.00%> (+0.09%)	:arrow_up:
compiler_gym/views/observation.py	96.87% <0.00%> (-3.13%)	:arrow_down:
compiler_gym/views/observation_space_spec.py	82.85% <0.00%> (-2.86%)	:arrow_down:
compiler_gym/envs/llvm/datasets/cbench.py	79.71% <0.00%> (-0.87%)	:arrow_down:
...ompiler_gym/service/client_service_compiler_env.py	90.44% <0.00%> (-0.43%)	:arrow_down:
compiler_gym/datasets/uri.py	100.00% <0.00%> (ø)
compiler_gym/compiler_env_state.py	100.00% <0.00%> (ø)
compiler_gym/datasets/benchmark.py	99.04% <0.00%> (+0.01%)	:arrow_up:
...loop_tool/service/loop_tool_compilation_session.py	90.54% <0.00%> (+0.67%)	:arrow_up:
... and 7 more

[ChrisCummins]

Fixes #750.