fix: Remove checks for unit zooms and symmetric rotations in template warp

[effigies]

A user with a custom template is generating warps that have spacing [1.5 1.5 1.5]: https://neurostars.org/t/use-custom-dartel-template-in-fmriprep/30670/8

The check for unit spacing was mostly intended to avoid weird behavior where we might generate a bad affine. The interpretation of isotropic spacing is straightforward, so I think we can relax this. Creating a docker image to allow for testing.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 71.77%. Comparing base (08933bf) to head (1607996).
Report is 3 commits behind head on maint/24.1.x.

Additional details and impacted files

@@               Coverage Diff                @@
##           maint/24.1.x    #3376      +/-   ##
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+ Coverage         71.70%   71.77%   +0.06%     
================================================
  Files                57       57              
  Lines              4259     4255       -4     
  Branches            640      459     -181     
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  Hits               3054     3054              
+ Misses             1090     1086       -4     
  Partials            115      115              

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[effigies]

I resampled the MNI T1w image to one with a shape of (193, 192, 229) and an affine of:

[[   0.     1.1    0.  -105.6]
 [   0.     0.    -1.2  118.8]
 [   1.     0.     0.   -78. ]
 [   0.     0.     0.     1. ]]

After registering the original image to the resampled image with antsRegistrationSyNQuick.sh (modified to produce a composite .h5 output), I was able to load it and verify that the reference it generated had the same shape and affine using the method we have here. I'm comfortable removing these checks.

That method is also reproduced in nitransforms 24+ (verified again), so we can move to that in 24.2.