arch: make deviceid moe felxible with cuda/rocm env vars

[mloubout]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 25.00000% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.40%. Comparing base (6c41641) to head (bfeebc4).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
tests/test_gpu_common.py	11.11%	8 Missing ⚠️
devito/operator/operator.py	42.85%	3 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2906   +/-   ##
=======================================
  Coverage   83.40%   83.40%           
=======================================
  Files         248      248           
  Lines       51625    51633    +8     
  Branches     4454     4457    +3     
=======================================
+ Hits        43056    43064    +8     
+ Misses       7815     7814    -1     
- Partials      754      755    +1     

Flag	Coverage Δ
pytest-gpu-aomp-amdgpuX	68.68% <25.00%> (-0.02%)	⬇️
pytest-gpu-gcc-	78.00% <0.00%> (-0.03%)	⬇️
pytest-gpu-icx-	77.64% <0.00%> (+0.01%)	⬆️
pytest-gpu-nvc-nvidiaX	69.22% <25.00%> (-0.03%)	⬇️

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[EdCaunt]

Seems reasonable - I would also update the FAQ to document this behaviour