bugfix: add support for multi-channel inputs for MR reconstruction models

[ad12]

This PR adds minimal support for multi-channel inputs for MR reconstruction and patches runtime errors seen in the skm-tea repository. Additional support will be provided in future PRs.

Note, in the short term, the SenseModel will support multi-channel inputs when only one set of maps for each coil is estimated. This will be fixed in #18

Changelist

• [x] permute the input in GeneralizedUNet when channels are reshaped
• [x] migrate recon models to use meddlr.forward.mri.SenseRecon instead of meddlr.utils.transforms.SenseRecon (deprecated)
• [x] update SenseModel to resolve differences between multi-channel inputs and multiple maps

[codecov-commenter]

Codecov Report

Merging #19 (2a00ed8) into main (296e6c3) will increase coverage by 0.02%. The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #19      +/-   ##
==========================================
+ Coverage   58.10%   58.13%   +0.02%     
==========================================
  Files          76       76              
  Lines        5607     5611       +4     
  Branches     1194     1196       +2     
==========================================
+ Hits         3258     3262       +4     
  Misses       2040     2040              
  Partials      309      309              

Flag	Coverage Δ
unittests	58.13% <100.00%> (+0.02%)	:arrow_up:

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Impacted Files	Coverage Δ
meddlr/ops/fft.py	45.00% <ø> (ø)
meddlr/forward/mri.py	77.14% <100.00%> (+2.94%)	:arrow_up:
meddlr/ops/complex.py	34.22% <100.00%> (ø)

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