Lazy loading and caching

[munrojm]

Adds lazy loading of resters alongside some caching to greatly speed up instantiation of MPRester.

[codecov-commenter]

Codecov Report

Patch coverage: 91.66% and project coverage change: +0.45% 🎉

Comparison is base (7109a44) 69.90% compared to head (40464e1) 70.36%.
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #842      +/-   ##
==========================================
+ Coverage   69.90%   70.36%   +0.45%     
==========================================
  Files          51       51              
  Lines        2429     2480      +51     
==========================================
+ Hits         1698     1745      +47     
- Misses        731      735       +4     

Files Changed	Coverage Δ
mp_api/client/routes/materials/__init__.py	88.23% <ø> (-0.34%)	⬇️
mp_api/client/mprester.py	65.74% <87.50%> (+0.68%)	⬆️
mp_api/client/routes/materials/materials.py	77.66% <96.96%> (+9.09%)	⬆️
mp_api/client/core/client.py	82.79% <100.00%> (ø)
mp_api/client/core/utils.py	61.81% <100.00%> (+1.44%)	⬆️

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