feat(someip): add server-side support (offer service, register method handlers)

[vtz]

Summary

The current jumpstarter-driver-someip driver (added in #391) provides client-side SOME/IP operations: RPC calls, service discovery, event subscription, and raw messaging. This is great for testing against ECUs.

However, there are test scenarios where the test harness itself needs to act as a SOME/IP server — offering services, registering method handlers, and publishing events — so the DUT (ECU) can discover and call the tester.

Use case

In a Body ECU integration test setup:

• The ECU runs SOME/IP services (door lock, lighting, speed sensor)
• The tester needs to also offer a service that the ECU can discover and interact with (e.g. a mock cloud gateway or a test-specific service)
• The tester needs to publish events that the ECU subscribes to

Currently this requires dropping down to opensomeip directly, bypassing Jumpstarter's remoting and lease model.

Proposed API additions

Method	Description
offer_service(service_id, instance_id)	Offer a service via SOME/IP-SD
stop_offer(service_id, instance_id)	Stop offering a service
register_method(service_id, method_id, handler)	Register an RPC method handler
publish_event(service_id, event_id, eventgroup_id, payload)	Publish an event notification

These would mirror the server-side API from opensomeip.SomeIpServer (register_method, service offering via SD config, event publishing).

Context

• opensomeip already supports both client and server modes
• The Jumpstarter DoIP driver is also client-only, but DoIP is inherently a client/tester protocol; SOME/IP is peer-to-peer
• Related: jumpstarter-driver-someip PR feat: add SOME/IP driver wrapping opensomeip Python binding #391