Refactor UNT0022 expression comparison to use recursive semantic analysis

[Copilot]

Checklist

• I have read the Contribution Guide ;
• There is an approved issue describing the change when contributing a new analyzer or suppressor ;
• I have added tests that prove my fix is effective or that my feature works ;
• I have added necessary documentation (if appropriate) ;

Short description of what this resolves:

Replaces string-based expression comparison with recursive semantic analysis using Roslyn's SemanticModel to correctly identify semantically equivalent expressions while distinguishing between different object instances.

Changes proposed in this pull request:

• Added AreExpressionsEquivalent() helper - Uses IsEquivalentTo() for syntactic equivalence and recursively compares member access chains using GetSymbolInfo() and SymbolEqualityComparer to ensure entire expression chains match semantically
• Recursive comparison logic - For member access expressions (e.g., instance.transform), compares both the member symbol AND recursively validates the base expression, preventing false matches between different object instances
• Updated DetectExpressionReuse() method - Now uses the improved semantic comparison to detect when expressions are reused in subsequent statements, regardless of syntax variations
• Added test coverage - Three new test cases verify semantic equivalence detection handles transform.position vs this.transform.position correctly while properly distinguishing instance.transform from go.transform

Example scenarios now handled correctly:

// Syntactic equivalence: recognized as operating on the same transform
this.transform.position = new Vector3(0, 1, 0);
transform.rotation = Quaternion.identity;  // ✓ Can be combined

// Different instances: correctly distinguished
instance.transform.position = go.transform.position;
go.transform.rotation = go.transform.rotation;  // ✓ Not combined (different transforms)

// Reuse detection with semantic equivalence
this.transform.position = Target.position;
transform.rotation = Quaternion.LookRotation(Target.position - transform.position, Vector3.up);  // ✓ Correctly detected as reusing position

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[sailro]

@copilot this is incomplete, because only checking symbols is not enough. Like for any GameObject Foo, Foo.transform.position and this.transform.position (inside a MonoBehaviour) are the same symbol: the property name position, declared in the type Transform. But they are not at all the same thing when executing the code.

Like SetPositionAndRotationTests.DistinctMemberExpression is going to fail with your code. You should make sure that all tests are passing before requesting a review.

[Copilot]

@copilot this is incomplete, because only checking symbols is not enough. Like for any GameObject Foo, Foo.transform.position and this.transform.position (inside a MonoBehaviour) are the same symbol: ...

Fixed in commit f3988c7. The comparison now recursively checks the entire expression chain:

• Uses IsEquivalentTo() for syntactic equivalence (transform vs this.transform)
• For member access, compares member symbols AND recursively compares base expressions
• This correctly distinguishes instance.transform from go.transform while still recognizing transform and this.transform as equivalent