gh-35279: `sage.categories`: Modularization fixes for imports
    
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### 📚 Description

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We should be able to import Python modules from `sage.categories` even
if implementation modules are not installed; that's the premise of the
distribution **sagemath-categories**.
Here we make changes to avoid module-level dependencies on some higher-
level functionality, such as symbolic functions, linear algebra, etc.
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#35275 takes care of some other imports.

Part of
- #29705

### 📝 Checklist

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### ⌛ Dependencies
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URL: #35279
Reported by: Matthias Köppe
Reviewer(s): Kwankyu Lee