[core] Rez plugins: Ensure dependencies for meshroom_compute are present

[cbentejac]

Description

This PR introduces a mechanism to ensure that required dependencies for meshroom_compute, specifically psutil, are always included in the node execution environment for rez plugins. Dependencies for meshroom_compute are added to the environment without specifying any version or attempting to match Meshroom's, in order for it to be set directly during the environment resolution.

Dependency management improvements:

• Introduced a new constant _MESHROOM_COMPUTE_DEPS in meshroom/core/desc/node.py to define required dependencies for meshroom_compute.
• Updated meshroom/core/plugins.py to import _MESHROOM_COMPUTE_DEPS and ensure all dependencies listed in it (currently psutil) are always included in the resolved execution environment for plugins, unless already present [1] [2].

[codecov]

Codecov Report

❌ Patch coverage is 25.00000% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.56%. Comparing base (e9e637d) to head (9b94471).
⚠️ Report is 3 commits behind head on develop.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
meshroom/core/plugins.py	14.28%	6 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #2898      +/-   ##
===========================================
- Coverage    79.62%   79.56%   -0.07%     
===========================================
  Files           51       51              
  Lines         6970     6977       +7     
===========================================
+ Hits          5550     5551       +1     
- Misses        1420     1426       +6     

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