Add new model vSHARP & CMR challenge along with 3D reconstruction code

[georgeyiasemis]

• vSHARP Model: Supporting both 2D and 3D. (Details: vSHARP Paper)
• CMRxRecon Challenge Code: Includes necessary code and dataset for the CMRxRecon challenge. Learn more about the challenge here.
• 3D Reconstruction Experiments: Various additions, such as transforms, engine changes (e.g., visualization), and the addition of new metrics and losses.
• Cartesian Subsampling Masks: Similar to FastMRI but with a twist - selection of the number of center lines instead of center fractions for ACS.
• Project Organization: Introduces new project folders for vSHARP and the CMRxRecon challenge.
• Model Zoo for CMRxRecon Winning Solution
• Minor Code Quality Enhancements

[codecov]

Codecov Report

Attention: 137 lines in your changes are missing coverage. Please review.

Comparison is base (2a4c293) 83.93% compared to head (174ed7d) 84.48%.

Files	Patch %	Lines
direct/data/datasets.py	79.59%	30 Missing ⚠️
direct/nn/mri_models.py	80.58%	20 Missing ⚠️
direct/data/mri_transforms.py	86.60%	15 Missing ⚠️
direct/functionals/hfen.py	81.08%	14 Missing ⚠️
direct/data/h5_data.py	14.28%	12 Missing ⚠️
direct/engine.py	25.00%	12 Missing ⚠️
direct/nn/vsharp/vsharp.py	92.40%	12 Missing ⚠️
direct/common/subsample.py	91.17%	6 Missing ⚠️
direct/nn/conv/conv.py	93.65%	4 Missing ⚠️
direct/functionals/snr.py	87.50%	3 Missing ⚠️
... and 4 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #254      +/-   ##
==========================================
+ Coverage   83.93%   84.48%   +0.55%     
==========================================
  Files          91       96       +5     
  Lines        6298     7316    +1018     
==========================================
+ Hits         5286     6181     +895     
- Misses       1012     1135     +123     

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[georgeyiasemis]

Thank you for the PR. Check my comments.

All checked! I also added readmes for the two new projects.