Type inference: Unify getABaseTypeMention and conditionSatisfiesConstraint

[hvitved]

This PR removes getABaseTypeMention, and instead ensures that sub-type relations expressed in terms of conditionSatisfiesConstraint are taken into account when matching types of arguments against types of parameters containing type parameters:

class A<T> {
    public T Get() { ... } // the implicit `this` parameter has type `A<T>`
}

class B : A<int> { ... }

new B().Get() // `int` is matched against `T` to infer that the type of the call is `int`

getABaseTypeMention was not in use in Rust, so this PR has no semantic effect on Rust, but for languages with type hierarchies, such as Swift, it means that we can treat type hierarchies in the same way that traits are treated in Rust.

#21837 has been used to verify this PR.

[hvitved]

Rerun has been triggered: 4 restarted 🚀

• Rust Integration tests MacOS (all)
• Java Integration tests MacOS (all)
• Java Language Tests Linux
• CPP Integration tests Linux

[hvitved]

Rerun has been triggered: 2 restarted 🚀

• Java Language Tests Linux
• CPP Integration tests Linux

[Copilot]

Pull request overview

This PR unifies type-hierarchy handling in the shared type inference library by removing getABaseTypeMention and relying on conditionSatisfiesConstraint for matching argument types against parameter types involving type parameters (covering both class hierarchies and Rust trait-style constraints).

Changes:

• Removed getABaseTypeMention from the shared InputSig2 interface and deleted the associated base-type-mention traversal logic.
• Reworked base-type matching to use the conditionSatisfiesConstraint hierarchy when inferring type arguments for accesses.
• Updated Rust’s type inference instantiations of InputSig2 to match the new interface (removing now-defunct stubs).

Show a summary per file

File	Description
shared/typeinference/codeql/typeinference/internal/TypeInference.qll	Removes the base-type-mention API and routes base-type inference through conditionSatisfiesConstraint; updates related documentation/comments.
rust/ql/lib/codeql/rust/internal/typeinference/TypeInference.qll	Drops getABaseTypeMention stub implementations to conform to the updated shared signature.

Copilot's findings

Comments suppressed due to low confidence (1)

shared/typeinference/codeql/typeinference/internal/TypeInference.qll:397

• In the Rust examples explanation, the sentence says “condition and condition are identical”; the second identifier should be constraint. Also “seconds example” should be “second example”.

     * the meaning is "`T` implements `Trait`" where the constraint is only
     * valid for the specific `T`. Note that `condition` and `condition` are
     * identical in the two examples. To encode the difference, `abs` in the
     * first example should contain `T` whereas in the seconds example `abs`
     * should be empty.

• Files reviewed: 2/2 changed files
• Comments generated: 1