Fixed gpu+cpu-based installation requirements

[tesfaldet]

What does this PR do?

Fixes gpu+cpu-based installation requirements in environment.yaml (conda-based install) and requirements.txt (pip-based install). Specifically, a gpu+cpu-based installation is assumed as the default method, and so for environment.yaml the necessary channels are added as well as the pytorch-cuda package. There's also an option for a cpu-only install. Similarly for a pip-based install, requirements.txt has the --extra-index-url specifier for specifying a gpu+cpu-based install or a cpu-only install, as taken from https://pytorch.org/get-started/locally/.

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yus

[tesfaldet]

Tests can be fixed from this PR #585

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (9355a5d) 83.66% compared to head (9c4f7d4) 83.66%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #586   +/-   ##
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  Coverage   83.66%   83.66%           
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  Files          11       11           
  Lines         355      355           
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  Hits          297      297           
  Misses         58       58           

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[ashleve]

Looking at the https://pytorch.org/get-started/locally/, only cuda 11.8 requires those lines, while 11.7 doesn't, and 11.7 is set as default when installing through normal pip install torch.

I think there's not much point in trying to maintain those instructions for requirements.txt as they seem to regulary change every couple of weeks/months. I would rather just leave this file simple and let people figure out what they need by themselves

[tesfaldet]

Yeah you're right. Perhaps I can add a comment that at least notifies the user of this, so it's not too painful for them to modify requirements.txt or environment.yaml