Rust: Add Operation class

[geoffw0]

Unify various classes representing operations under a single Operation class, providing a single consistent interface (with getOperatorName() and getAnOperand()) for reasoning about them.

The idea is to get things in order before I follow up with another PR that will add new subclasses, allowing us to find things like the dereference expression (*) and comparison operations more easily.

[Copilot]

Pull Request Overview

This PR introduces a unified Operation class in the Rust QL library, letting all unary, binary, assignment, and logical expressions share a consistent interface with getOperatorName() and getAnOperand().

• Defined OperationImpl::Operation and aliased it as Operation
• Updated PrefixExpr and BinaryExpr implementations to mix in Operation
• Added imports of Operation in query modules and extended tests to exercise the new API

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

File	Description
rust/ql/lib/codeql/rust/elements/Operation.qll	Added the abstract Operation class and alias
rust/ql/lib/codeql/rust/elements/internal/PrefixExprImpl.qll	Extended PrefixExpr to implement Operation
rust/ql/lib/codeql/rust/elements/internal/BinaryExprImpl.qll	Extended BinaryExpr to implement Operation
rust/ql/test/library-tests/operations/test.rs	Expanded inline tests for various operators

Comments suppressed due to low confidence (1)

rust/ql/test/library-tests/operations/test.rs:54

• No inline expectation is provided for the ? try operator. Consider adding an expectation comment, for example: // $ Operation Op=? Operands=1 PrefixExpr to validate its classification and operands.

res?;

[geoffw0]

DCA shows nothing interesting, which is what we'd expect for a change like this.