[TS] Return function from typeof callable values

[CaelmBleidd]

Closes #429

Change

typeof now identifies concrete callable references represented by associatedFunction or an exact EtsFunctionType before checking string/object types. This also avoids the type-constraint null dereference on untyped method references.

Evidence

• Source-level regressions use the existing TypeOf : TsMethodTestRunner and discoverProperties pattern. They cover an arrow, a function expression, a callable stored in a local and in an object field, a named function, and a symbolic boolean selecting between a callable and an ordinary object. Invariants reject unexpected results, and the conditional test requires both branches.
• Local: :usvm-ts:test --tests org.usvm.samples.operators.TypeOf — 21 passed, 1 disabled. :usvm-ts:detektTest and git diff --check passed.
• Negative control: with the TsExprResolver change removed, test typeOfArrow fails because the old typeof path throws a NullPointerException and produces no analysis result. Restoring the change makes it pass.
• All seven CI checks passed on the updated head 7ad0b2a0c03a234ab49d653a3775d1568574a533 (including ci-ts and detekt).

Boundary

Function-typed input parameters are tracked separately in #462: TsInterpreter.getInitialState passes EtsFunctionType to EtsHierarchy.classesForType, which throws before typeof executes. The existing input-function test remains disabled with this precise reason. Imported functions are also outside the represented concrete callable cases.