perf(artifacts): cache artifact manifests and prefer loading to downloading

[moredatarequired]

Description

• Fixes WB-NNNNN

• Fixes #NNNN

• add a cache specifically for manifests, stored under the committed artifact ID

• _load_manifest now checks the manifest cache

  • if the manifest exists, it doesn't download from the URL
  • if it doesn't, it saves the manifest after downloading it

• I updated CHANGELOG.md, or it's not applicable

Testing

How was this PR tested?

[codecov]

Codecov Report

Attention: Patch coverage is 95.45455% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 74.77%. Comparing base (4e6da66) to head (06def8d).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7435      +/-   ##
==========================================
- Coverage   75.87%   74.77%   -1.10%     
==========================================
  Files         517      517              
  Lines       54545    54561      +16     
==========================================
- Hits        41385    40800     -585     
- Misses      12778    13376     +598     
- Partials      382      385       +3     

Flag	Coverage Δ
func	43.25% <90.90%> (+0.01%)	⬆️
system	62.15% <95.45%> (-1.83%)	⬇️
unit	57.63% <31.81%> (-0.01%)	⬇️

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

Files	Coverage Δ
wandb/sdk/artifacts/artifact.py	80.31% <100.00%> (-12.94%)	⬇️
wandb/sdk/artifacts/artifact_file_cache.py	92.42% <85.71%> (-0.49%)	⬇️

... and 38 files with indirect coverage changes