Small refactoring before adding multiple representations

[katehryhorenko]

BACKGROUND: I'm planning to re-use code that creates Csg.Solid from SolidOperation

DESCRIPTION: Solid creation is moved to a separate class

TESTING:

• I tested it on a few functions. I can share them with you.

REQUIRED:

• [ ] All changes are up to date in CHANGELOG.md.

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This change is