Add model-zoo for pretrained models

[ad12]

This PR includes 1) a workflow for fetching pretrained models and 2) a list of pretrained models pertaining to different projects.

• [x] Add meddlr.get_model_from_zoo function to fetch pretrained models hosted on gdrive
• [x] Add load_weights to load weights into the fetched models
• [x] Added Noise2Recon and VORTEX pretrained models
• [x] Clean up meddlr README, add instructions to use model zoo
• [x] Update Noise2Recon/VORTEX readmes with proper proper link, list of pre-trained models

[codecov-commenter]

Codecov Report

Merging #27 (6a9a051) into main (85ab1a3) will increase coverage by 0.14%. The diff coverage is 70.76%.

@@            Coverage Diff             @@
##             main      #27      +/-   ##
==========================================
+ Coverage   70.72%   70.87%   +0.14%     
==========================================
  Files          70       71       +1     
  Lines        4680     4745      +65     
  Branches     1019     1036      +17     
==========================================
+ Hits         3310     3363      +53     
- Misses       1049     1056       +7     
- Partials      321      326       +5     

Flag	Coverage Δ
unittests	70.87% <70.76%> (+0.14%)	:arrow_up:

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Impacted Files	Coverage Δ
meddlr/config/config.py	76.11% <40.00%> (+2.47%)	:arrow_up:
meddlr/engine/model_zoo.py	72.88% <72.88%> (ø)
meddlr/__init__.py	100.00% <100.00%> (ø)
meddlr/config/util.py	96.42% <0.00%> (+3.57%)	:arrow_up:

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