Add a CallbackToken service so we can move it out of the service_bus_provider module

Generated with the help of an LLM.

Problem/Motivation

The current service_bus_provider module contains call token code that needs to be shared so other providers can use it. This issue is to add that code to service_queue so it can be safely removed from service_bus_provider.

See also #3638216: Migrating CallToken code to service_queue module so it can be shared

Proposed resolution

I will create an MR.

Remaining tasks

None.

User interface changes

None.

API changes

None.

Data model changes

None.